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Building blocks: 96 3D models

Single units to repeat with Arrange in a shape: lipids and bilayer tiles, membrane proteins, nucleotides and DNA turns, protein subunits, ions and small molecules, polymer pieces and tissue cells (real sizes 0.1 nm–µm). Each one is a ready-made 3D model you can turn, recolour and place in a figure — open BioDiorama and type its name in the Library search.

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Membrane lipids · Membrane proteins · Nucleic acids · Proteins · Small molecules & ions · Polymers & materials · Nanoparticle units · Cell units (tile into tissues)

Membrane lipids 20

Phospholipid (single) — One glycerophospholipid: a head group on a phosphate and glycerol, with two fatty-acid tails. Choose the head group (PC, PE, PS, PG, PA, PI), tail length and how many tails are kinked by cis double bonds. Head points +Z. (≈ 2.6 nm long)
Lysophospholipid (one tail) — A phospholipid that has lost one tail (lyso-PC, LPA): a big head on a single chain, so it is cone-shaped — it makes membranes curve and forms micelles. Head +Z. (≈ 2.5 nm long)
Cholesterol (single) — Cholesterol as it sits in a membrane: a small hydroxyl head, a rigid flat plank of four fused rings and a short branched tail. It packs between phospholipid tails, stiffening the membrane and forming rafts. OH points +Z. (≈ 1.9 nm long)
Sphingomyelin (single) — A sphingolipid: phosphocholine head on a sphingosine backbone with an amide-linked, usually long and saturated, fatty acid. With cholesterol it forms ordered lipid rafts. Head +Z. (≈ 2.8 nm long)
Ceramide (single) — The simplest sphingolipid: a sphingosine chain and a fatty acid with only small hydroxyl and amide groups as a head. The main lipid of the skin barrier and a signal of cell stress. Head +Z. (≈ 2.4 nm long)
Glycolipid (sugar head) — A sphingolipid with a sugar head, drawn with the standard glycan symbols: one galactose (cerebroside), a chain of four sugars (globoside) or the branched head of ganglioside GM1 with its sialic acid. They face outward on the cell surface. Head +Z. (≈ 3–5 nm long)
PEG-lipid — A lipid carrying a polyethylene glycol chain (like DSPE-PEG2000 or DMG-PEG): the lipid anchors in the membrane and the PEG forms a water-loving coil — a "mushroom" at low density, a stretched "brush" when crowded. It gives stealth liposomes and LNPs their coat. Head +Z. (PEG2000 coil ≈ 3.5 nm across)
Cationic lipid — A permanently positive lipid (like DOTAP or DOTMA): a small quaternary-ammonium head with a + charge on two unsaturated tails. It binds DNA and RNA in lipoplexes. Head +Z. (≈ 2.6 nm long)
Ionizable lipid (LNP) — The key lipid of mRNA lipid nanoparticles: a small amine head that is neutral in blood but turns positive (+) in acidic endosomes, on branched tails that splay into a cone — this shape helps it break the endosome membrane. Head +Z. (≈ 2.5 nm long)
Detergent / surfactant — A single-tailed surfactant that dissolves membranes into micelles. Choose an ionic one (SDS, with a − sulfate head), a non-ionic one with a polyethylene-glycol head (Triton X-100 / polysorbate type), a sugar-headed one (DDM) or the steroid-based zwitterion CHAPS. Head +Z. (≈ 1.5–3 nm long)
Fatty acid — A free fatty acid: a carboxyl head (COOH, or COO⁻ when ionised) on one hydrocarbon chain — straight when saturated (palmitic, stearic), bent once when monounsaturated (oleic) or curled when polyunsaturated (EPA, DHA). Head +Z. (≈ 2 nm long)
Triglyceride (fat) — A triacylglycerol: three fatty acids on a glycerol, shaped like a trident. The storage fat of adipocytes and the core of lipid droplets, chylomicrons and lipid nanoparticles such as NLCs. Glycerol +Z. (≈ 2 nm)
Phosphoinositide (PIP₂ / PIP₃) — A signalling lipid of the inner leaflet: an inositol ring head carrying extra phosphates — PI(4,5)P₂ with two, PI(3,4,5)P₃ with three — on a saturated and an arachidonic (curly) tail. Head +Z. (≈ 2.8 nm long)
Cardiolipin (four tails) — The double phospholipid of the inner mitochondrial membrane (and bacteria): two phosphates bridged by a glycerol, carrying four tails — a wide cone that gathers where the membrane bends, such as crista tips. Head +Z. (≈ 2.6 nm long, 1.3 nm wide)
Archaeal lipid (membrane-spanning) — A tetraether lipid of archaea: two head groups joined by two long branched isoprenoid chains that span the whole membrane, making a tough monolayer that survives heat and acid. Origin on the membrane midplane. (≈ 5 nm long)
Lipopolysaccharide (LPS) — The molecule of the Gram-negative outer leaflet: lipid A (six tails on two phosphorylated glucosamines — the endotoxin), a core oligosaccharide and an O-antigen of repeating sugar units ("smooth" LPS; "rough" LPS has none). Sugar chain +Z. (≈ 2 nm lipid A + sugar chain up to ~20 nm)
Lipid patch (2 × 2) — Four phospholipids side by side, heads up — a small monolayer piece. Arrange it on a surface for a quick, light monolayer, or flip a second copy under it for a bilayer. Origin in the middle of the molecules. (1.6 × 1.6 nm)
Lipid bilayer tile (seamless) — A square piece of lipid bilayer that tiles without seams: copies placed side by side every n × 0.8 nm (its width) join into one membrane. Choose plain PC, a mixed membrane, or an asymmetric plasma membrane (PC, sphingomyelin and cholesterol outside; PE and PS inside). Origin on the bilayer midplane, outer leaflet +Z. (n × 0.8 nm square, 5 nm thick)
Lipid raft tile (seamless) — A seamless tile of ordered membrane: sphingomyelin with long straight tails packed with cholesterol in the outer leaflet, saturated lipids and cholesterol inside — slightly thicker than the surrounding membrane. Mix it with the bilayer tile to draw rafts. Origin on the midplane, outside +Z. (n × 0.8 nm square, ≈ 5.5 nm thick)
Vesicle (smooth, light) — A light, smooth membrane vesicle for drawing many at once — synaptic vesicles, transport vesicles, small liposomes or exosomes. Cut it open to show the 5 nm bilayer (heads and tails) and the lumen. Origin at the centre. (30–200 nm)

Membrane proteins 19

G-protein-coupled receptor (single) — A seven-transmembrane receptor drawn as seven helix cylinders joined by loops, the N-terminus outside (+Z) and helix 8 lying along the inner surface. Add a ligand in its pocket; dock a G protein under it. Origin on the membrane midplane. (≈ 4 × 4 × 7 nm)
Receptor tyrosine kinase — A single-pass receptor such as EGFR or the insulin receptor family: ligand-binding domains outside, one transmembrane helix and a kinase domain inside. As an active dimer its ligands are bound and its tails phosphorylated (orange). Origin on the membrane midplane. (≈ 15 nm tall)
Ion channel (single) — A pore-forming channel seen from the side: a K⁺ channel (four subunits, inverted teepee), a ligand-gated channel (five tall subunits, like the nicotinic receptor) or a voltage-gated Na⁺/Ca²⁺ channel (four domains with voltage-sensor paddles). Open or closed, with an ion in the pore. Origin on the membrane midplane. (≈ 6–8 nm across)
Transporter (carrier) — A carrier that moves its substrate by rocking between two halves: open to the outside, closed around the substrate (occluded), or open to the inside — the alternating-access cycle of glucose transporters, symporters and antiporters. Origin on the membrane midplane. (≈ 5 × 4 × 6 nm)
β-barrel porin — An outer-membrane β-barrel (porin, OmpF, VDAC): β-strands running at a slant round a water-filled pore, loops on the outside. Choose 8 strands (OmpA), 16 (porin) or 19 (VDAC of mitochondria). Origin on the membrane midplane. (≈ 3–5 nm across)
Integrin (αβ heterodimer) — The cell-adhesion receptor that grips the extracellular matrix: an α subunit (β-propeller head) and a β subunit (βI domain) on long legs with two transmembrane helices. Inactive integrins are bent over; active ones stand up with the head open. Origin on the membrane midplane. (≈ 20 nm tall when extended)
Cadherin — A classical cadherin of adherens junctions: five extracellular repeats in a gentle arc, held rigid by calcium ions (yellow) between them, one transmembrane helix and a cytoplasmic tail with β-catenin bound. Copies on facing cells meet tip to tip. Origin on the membrane midplane. (≈ 25 nm tall)
Tetraspanin (CD9 / CD63 / CD81) — A small four-transmembrane protein with a mushroom-like large extracellular loop. Tetraspanins organise membrane microdomains and mark exosomes (CD9, CD63, CD81). Origin on the membrane midplane. (≈ 4 × 3 × 7 nm)
GPI-anchored protein — A surface protein held only by a glycosylphosphatidylinositol (GPI) anchor: two lipid tails in the outer leaflet, a short sugar stalk and the protein above (like CD55, CD59, alkaline phosphatase or prion protein). It gathers in rafts. Origin on the membrane midplane. (≈ 8 nm tall)
Connexon (gap-junction hemichannel) — Six connexin subunits ringed round a central pore. A connexon in one cell docks to one in the next to make a gap-junction channel that lets ions and small molecules pass. Origin on the membrane midplane. (≈ 7 nm across, 7.5 nm tall)
Na⁺/K⁺-ATPase (pump) — The P-type pump that keeps sodium out and potassium in, spending one ATP for three Na⁺ out and two K⁺ in: an α subunit (transmembrane domain plus the A, N and P domains inside) and a glycosylated β subunit. Origin on the membrane midplane. (≈ 6 × 6 × 15 nm)
ABC transporter (efflux pump) — An ATP-binding-cassette pump such as P-glycoprotein (MDR1) or CFTR: two transmembrane wings that open inward to take up a drug, and two nucleotide-binding domains below that clamp shut on ATP to flip it outward — a major cause of multidrug resistance. Origin on the membrane midplane. (≈ 6 × 5 × 13 nm)
Toll-like receptor (TLR) — A pattern-recognition receptor of innate immunity: a horseshoe-shaped leucine-rich-repeat ectodomain that binds microbial molecules (LPS, flagellin, RNA, CpG DNA), one transmembrane helix and a TIR signalling domain inside. As an active dimer, two horseshoes hold the ligand between them. Origin on the membrane midplane. (≈ 15 nm tall)
Chimeric antigen receptor (CAR) — The engineered receptor of CAR-T cells, built from parts: an scFv that binds the tumour antigen, a hinge, a transmembrane helix, then (2nd/3rd generation) one or two co-stimulatory domains (CD28, 4-1BB) and the CD3ζ chain with its three ITAMs. Origin on the membrane midplane. (≈ 15 nm tall)
Ig-superfamily receptor — A single-pass surface receptor made of immunoglobulin-like domains stacked on a stalk — choose one domain (PD-1), two (PD-L1, CD28), four (CD4) or five (ICAM-1), with or without sugar chains. Origin on the membrane midplane. (≈ 4–30 nm tall)
MHC with peptide — A major-histocompatibility-complex molecule presenting a peptide (orange) in the groove between two helices. Class I (all nucleated cells, to CD8 T cells) has a heavy chain with β₂-microglobulin; class II (antigen-presenting cells, to CD4 T cells) has α and β chains. Origin on the membrane midplane. (≈ 7 nm above the membrane)
T-cell receptor (TCR–CD3) — The T-cell antigen receptor: the αβ TCR (four Ig domains; its tips touch the peptide–MHC) with the CD3εγ and CD3εδ dimers alongside and the ζζ chains inside carrying the signalling ITAMs. Origin on the membrane midplane. (≈ 9 nm above the membrane)
BAR-domain dimer (membrane bender) — A banana-shaped dimer (amphiphysin, endophilin, F-BAR proteins) whose positively charged concave face grips and bends the membrane — used at endocytic necks and tubules. Peripheral: the origin is on the membrane-binding face, which points +Z (the protein hangs below, on the cytoplasmic side). (≈ 20 nm long)
Clathrin triskelion — The three-legged unit of the clathrin coat: three heavy chains meet at a hub, each leg bent at the knee and ending in a terminal domain, with light chains on the inner legs. Many interlock into the cage of a coated pit or vesicle. Origin at the hub; the legs pucker towards −Z, where the membrane is. (≈ 50 nm leg span)

Nucleic acids 8

Nucleotide (single) — One nucleotide as figures draw it: a phosphate (orange bead), the sugar (pentagon) and the base (one ring for C, T and U; two for A and G) pointing +X. For RNA the sugar carries the extra 2′-OH (red). Many in a row make a strand. (≈ 1 nm)
Base pair (rung) — One rung of the DNA ladder: two complementary bases held by hydrogen bonds (two for A–T and A–U, three for G–C), each on its sugar–phosphate backbone bead. Lies along X; stack copies 0.34 nm apart, turning 36° each, for a helix. (≈ 2 nm across)
DNA turn (tiles end to end) — One (or a few) helical turns of B-DNA — 10 base pairs per turn, 3.4 nm long, both grooves — that join seamlessly when copies are placed end to end along Z. Colour the bases by letter or in one colour; show phosphates as beads. (3.4 nm per turn, 2 nm wide)
DNA end (blunt or sticky) — A short duplex ending in a blunt cut or a sticky end — a 4-nt single-stranded overhang on the 5′ or 3′ strand, as left by restriction enzymes (EcoRI, PstI) — for cloning, ligation and Gibson-assembly figures. The end points +Z. (≈ 4 nm)
DNA ladder (flat, schematic) — Untwisted DNA drawn as a ladder: two backbone rails with coloured base-pair rungs, for schematic figures of sequences, mutations and editing. Copies tile end to end along Z. (0.6 nm per rung)
Single strand segment (RNA / ssDNA) — A short single-stranded stretch with its bases stacked on one side of a gentle helix (11 nucleotides per turn, like A-form RNA), tiling end to end along Z — for mRNA, guide RNA, primers and probes. Choose RNA (with U) or single-stranded DNA. (≈ 3 nm per 11 nt)
Histone octamer — The protein spool of the nucleosome: two each of histones H3, H4, H2A and H2B, with their flexible tails (where acetyl and methyl marks go) sticking out. DNA wraps round its rim. Disc axis Z. (≈ 6.5 nm across)
Nucleosome with linker DNA — One bead of the "beads on a string": 147 bp of DNA wrapped 1.65 turns round a histone octamer, with straight linker DNA leaving along −X and +X so copies placed in a row (every length along X) join into a chromatin fibre. Optional linker histone H1. (11 nm bead + linkers)

Proteins 21

Amino acid (bead) — One amino-acid residue as a bead on the backbone with its side chain as a smaller bead, coloured by property (hydrophobic, polar, positive, negative, aromatic or special). The backbone stubs along ±Z let copies placed in a row join into a peptide chain. (≈ 0.8 nm)
α-helix segment (with side chains) — An α-helix as a coiled ribbon with its side chains sticking out (3.6 residues per turn, 0.15 nm rise each). Each piece is a whole number of turns, so copies tile end to end along Z; colour side chains by one colour or as an amphipathic helix (one face hydrophobic). (0.54 nm per turn, ≈ 1.2 nm wide)
β-hairpin (two strands) — Two antiparallel β-strands joined by a tight turn — drawn as flat arrows — the smallest piece of a β-sheet. Copies side by side make a sheet; many stacked along Z make an amyloid-like fibril. (≈ 2.5 × 1 nm)
Coiled coil (tiles end to end) — Two (or three) α-helices wound round each other — the leucine zipper of transcription factors, the stalks of myosin and kinesin, and intermediate filaments. Each piece is whole supercoil repeats, so copies join seamlessly along Z. (≈ 2 nm wide, 3.5 nm per repeat)
Protein (light, sized by mass) — A light, lumpy globular protein sized from its mass (radius ≈ 0.066·kDa^⅓ nm): 15 kDa (lysozyme), 66 kDa (albumin), 150 kDa (antibody-sized) and beyond. Made for crowds — cytoplasm, plasma, a protein corona — where hundreds are needed. Shuffle for a new shape. (≈ 3–10 nm)
G-actin (monomer) — One actin subunit: four lobes (subdomains 1–4) round a deep cleft holding ATP or ADP. Filaments grow by adding copies along a twisting two-start helix (rise 2.75 nm, turn −167°); the pointed end is +Z, the barbed end −Z. (≈ 5.5 × 5.5 × 3.5 nm)
Tubulin dimer (α/β) — The building block of microtubules: an α-tubulin and a β-tubulin, each ~4 nm, joined head to tail with GTP bound. Thirteen protofilaments of these make a microtubule; β faces the plus end (+Z). (8 nm long)
Ubiquitin — The 76-residue tag that marks proteins for the proteasome or for signalling: a compact β-grasp fold with a flexible C-terminal tail (Gly-Gly) that links it to a lysine on the target or on another ubiquitin. The tail points −Z. (≈ 2.5 nm)
Protein kinase — The typical kinase fold: a small N-lobe and a larger C-lobe with ATP in the cleft between them, the activation loop (orange) on the C-lobe and the substrate peptide in its groove. Kinase inhibitor drugs sit where the ATP is. (≈ 5 nm)
Heterotrimeric G protein (αβγ) — The switch under a GPCR: Gα (a Ras-like and a helical domain, GDP or GTP bound), Gβ (a seven-bladed propeller) and Gγ, both α and γ held to the membrane by lipid anchors. The anchors point +Z, so the trimer docks under a receptor. (≈ 7 nm)
Cytokine (four-helix bundle) — A small signalling protein with the four-helix-bundle fold of IL-2, IL-4, IL-6, GM-CSF, interferons, growth hormone and EPO (up-up-down-down helices joined by long loops). Scatter copies for a cytokine storm or a secretion figure. (≈ 2.5 × 4 nm)
Calmodulin with Ca²⁺ — The calcium sensor: two small lobes joined by a long central helix, each lobe holding two Ca²⁺ ions (yellow). With calcium bound it wraps round target helices to switch them on. Long axis Z. (≈ 6.5 nm long)
Green fluorescent protein (β-barrel) — GFP and its relatives (mCherry, YFP…): an 11-stranded β-barrel can with the glowing chromophore held in its middle. Choose the colour of the fluorescence. Barrel axis Z. (≈ 2.4 × 4.2 nm)
Fibrinogen — The clotting protein: a central E nodule joined by coiled-coil rods to two D nodules at the ends (trinodular), with flexible αC regions. Thrombin cuts it into fibrin, which stacks half-staggered into fibres. Long axis Z. (≈ 45 nm long)
Laminin (cross-shaped) — The cross-shaped glycoprotein of every basement membrane: three short arms with globular ends that link into a network, and a long coiled-coil arm ending in the LG domains that bind integrins and dystroglycan on cells. Long arm −Z. (≈ 70 nm long)
C1q (bouquet of tulips) — The first protein of the classical complement pathway: six collagen-like stalks joined at the base that splay out to six globular heads, each able to grab the Fc of an antibody bound to a microbe. Heads +Z. (≈ 30 nm tall)
DNA polymerase on DNA — A polymerase drawn as the classic right hand — palm (blue), fingers (green) and thumb (red) — gripping primer–template DNA, with an incoming nucleotide (yellow) in the active site. Works for replication, PCR and reverse transcriptase figures. (≈ 10 nm)
Protein ring (oligomer) — A ring of identical subunits — a hexameric helicase or AAA+ ATPase, a PCNA clamp (3), the Hfq or Lsm ring (6–7), a GroEL heptamer (7) or a pore-forming toxin (up to 14). Choose how many; optionally thread DNA through the middle. Ring axis Z. (≈ 8–20 nm across)
Antibody fragment (Fab, scFv, nanobody) — The smaller binders cut or engineered from antibodies: a Fab (heavy and light chain, four domains), F(ab′)₂ (two Fabs at the hinge), an scFv (two variable domains on a linker) or a single-domain nanobody (VHH, from camelids). Binding tips point +Z. (≈ 2.5–9 nm)
Mucin (bottlebrush glycoprotein) — A long protein backbone densely coated with short O-linked sugar chains, like a bottlebrush — the gel of mucus (MUC2, MUC5AC) or, membrane-tethered (MUC1), the tall shield of the glycocalyx. Also stands for proteoglycans such as aggrecan. Long axis Z. (≈ 20–200 nm)
Streptavidin with biotin — The tetramer that grips biotin more tightly than almost any other pair — the glue of bioconjugation, ELISA and labelling. Four β-barrel subunits, each with a biotin pocket (yellow) open on the surface. (≈ 5 nm)

Small molecules & ions 10

Ion (with charge) — One ion as a coloured sphere with its charge written on it (front and back): Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, H⁺, Zn²⁺, Fe²⁺/Fe³⁺, Cu²⁺, Li⁺, bicarbonate, phosphate or sulfate. Sizes follow the real ionic radii; add the shell of water molecules around it if you like. (≈ 0.4–0.9 nm (drawn ~1.5× real))
Water molecule (space-filling) — H₂O as a smooth space-filling shape: one oxygen (red) with two hydrogens (white) at 104.5°, optionally with δ− and δ+ partial charges. Scatter hundreds for solvent, or ring them round an ion. Hydrogens point −Z. (≈ 0.3 nm)
Gas molecule (space-filling) — A small gas molecule drawn space-filling in the usual atom colours: O₂, CO₂, N₂, NO, CO, H₂, CH₄, H₂S or ozone — for respiration, gas exchange, signalling and atmosphere figures. Long axis X. (≈ 0.3–0.4 nm)
Sugar (ring) — A monosaccharide drawn as its ring — a six-membered pyranose (glucose, galactose, mannose) or five-membered furanose (fructose, ribose) — with its hydroxyls as small beads. Coloured like the glycan symbol of that sugar. Ring in the XZ plane. (≈ 0.6 nm)
ATP / ADP / AMP / GTP / cAMP — The energy and signalling nucleotides drawn simply: the base (two rings), the ribose (pentagon) and a tail of phosphate beads — three for ATP and GTP, two for ADP, one for AMP, or the closed ring of cyclic AMP. Phosphate tail points +X. (≈ 1.4 nm)
Heme / chlorophyll (porphyrin) — A flat porphyrin ring with a metal in the middle: heme (iron, red-brown; in haemoglobin, myoglobin and cytochromes) or chlorophyll (magnesium, green, with its long phytol tail that anchors it in the thylakoid membrane). Ring in the XY plane. (≈ 1 nm disc)
Small molecule (blob) — A drug, metabolite, ligand or neurotransmitter as a smooth molecular-surface blob — choose a silhouette (round, oblong, flat, branched, three-armed or kidney) and colour. Real molecules (by name) come from the PubChem search; this is the simple stand-in for figures. (≈ 0.6–1.2 nm)
Drug molecule (flat fused rings) — A flat aromatic drug or dye drawn as its fused rings — one, two (naphthalene-like), three in a row (anthracene, like doxorubicin's core) or three bent (phenanthrene, like a steroid) — with a side group. A clear, non-ball-and-stick way to show an intercalator or planar drug. (≈ 1 nm)
Fluorescent dye (glowing) — A small fluorophore with a soft glow — FITC, rhodamine, Cy3/Cy5, DAPI, Alexa Fluor-type labels. Choose the emission colour; scatter copies to show labelling or release of a fluorescent cargo. (≈ 1 nm)
Cyclodextrin (sugar cone) — A ring of 6, 7 or 8 glucose units (α, β, γ-cyclodextrin) shaped like a truncated cone with a greasy cavity that hides a drug molecule inside — used to dissolve poorly soluble drugs. Wide rim +Z. (≈ 1.5 nm across)

Polymers & materials 10

Monomer bead (with bond stubs) — One repeat unit of a polymer: a bead with two bond stubs along ±Z, so copies placed in a row, round a ring or along a drawn path read as a chain. Pick the colour per block for copolymers. (any (≈ 1 unit))
Polymer chain segment (tiles end to end) — A flexible random-coil segment that starts at −Z and ends at +Z on the axis, so copies joined end to end make one long tangled chain — for polymer melts, hydrogels, PEG and unfolded proteins. Shuffle for a different coil. (length setting)
Block copolymer (amphiphile) — A diblock copolymer such as PEG–PLA or PEG–PLGA: a water-loving block (blue coil) joined to a water-fearing block (yellow, more compact). Arranged with the hydrophilic block +Z on a sphere they make a polymeric micelle; as a bilayer, a polymersome. (≈ 6–15 nm)
PEG chain (grafted) — A polyethylene glycol chain grafted to a surface at its anchor (the origin, flat side down), as a loose "mushroom" coil or a stretched "brush" — scatter it over a nanoparticle or surface for a PEG corona. Points +Z. (≈ 2–10 nm)
Crosslink node (network junction) — A junction of a polymer network — the point where 3, 4 or 6 strands meet (a tetra-PEG node, a chemical crosslink or a physical junction) with short strand stubs. Repeat in a grid or scatter in a volume for a hydrogel network. (≈ 2–4 nm)
Hydrogel mesh tile (seamless) — A cube of polymer network — wavy strands between junctions on a regular lattice — that tiles seamlessly in X, Y and Z, so copies stacked side by side fill any volume with one continuous hydrogel. Choose the mesh size and how wavy the strands are. (cube of side = mesh × cells)
Fibre segment (tiles end to end) — A straight piece of fibre that joins seamlessly end to end along Z: a collagen fibril with its 67 nm D-banding, a smooth polymer or electrospun fibre, a twisted bundle of fibrils, or a beaded fibre. Repeat along a curve for long fibres. (diameter and length settings)
Glycan symbol (3D, SNFG) — One sugar residue as its standard 3D glycan symbol (SNFG): blue sphere glucose, green mannose, yellow galactose, blue/yellow cubes GlcNAc/GalNAc, red cone fucose, purple diamond sialic acid, orange star xylose. Chain copies for any glycan. (≈ 0.7 nm)
N-glycan tree — A branched N-linked sugar tree in glycan symbols, as found on almost every secreted and surface protein: complex biantennary (with galactose and sialic acid caps), high-mannose, or just the core. Grows +Z from its asparagine link at the origin. (≈ 3–5 nm)
Peptidoglycan tile (cell wall) — A seamless tile of bacterial cell wall: glycan strands of alternating NAG (blue) and NAM (purple) running along X, cross-linked by short peptide bridges (orange) — the target of penicillin and lysozyme. Stack 1 layer for Gram-negative, many for Gram-positive. (n × 1 nm square)

Nanoparticle units 2

Nanoparticle (light) — A light nanoparticle for drawing many at once: choose the material (gold, silver, mesoporous silica, iron oxide, polymer, lipid, quantum dot, carbon), the size and an optional coat of PEG or targeting ligands. Detailed single nanoparticles are in the Nanoparticles category. (10–200 nm)
Capsomer (virus capsid unit) — The unit that tiles a virus capsid: a penton (five subunits, at the 12 vertices of an icosahedral capsid) or a hexon (six subunits, everywhere else), each a ring of protein around a small central channel. Outer face +Z. (≈ 8–12 nm)

Cell units (tile into tissues) 6

Columnar epithelial cell (hexagonal) — A tall epithelial cell shaped as a rounded hexagonal column, nucleus near the base, optional microvilli on top (+Z). Hexagons tile edge to edge: copies in a honeycomb grid (spacing √3 × radius) make a seamless columnar epithelium — gut, airway, kidney tubule. (≈ 8 × 25 µm (1 unit = 1 µm))
Cuboidal epithelial cell — A cube-shaped epithelial cell with a round central nucleus — kidney tubules, thyroid follicles, gland ducts. Rounded square sides tile edge to edge in a square grid every width. (≈ 10 µm cube (1 unit = 1 µm))
Squamous cell (flat) — A thin, flat polygonal cell with a bulging nucleus — the endothelium lining vessels, alveolar type I cells, mesothelium and the surface of skin. Flat hexagons tile edge to edge into a pavement. Nucleus bulge +Z. (≈ 30 × 3 µm (1 unit = 1 µm))
Round cell (simple) — A light, round cell with a nucleus — for crowds of blood cells, lymphocytes, suspension cultures, tumour cells or a spheroid made by arranging copies in a ball. Shuffle for a slightly different shape. (≈ 7–20 µm (1 unit = 1 µm))
Spindle cell (fibroblast / smooth muscle) — A long cell tapering to both ends with an elongated nucleus — a fibroblast, smooth-muscle cell or myofibroblast. Arrange copies along lines or in staggered rows for connective tissue, a vessel wall or aligned cultures. Long axis Z. (≈ 60 × 8 µm (1 unit = 1 µm))
Adipocyte (fat cell) — A white fat cell: one huge lipid droplet filling the cell, a thin rim of cytoplasm and a flattened nucleus pressed to the edge (signet-ring look). Pack copies in a ball or grid for adipose tissue. Nucleus +Z. (≈ 50–150 µm (1 unit = 1 µm))