Also: CapsidNet, how flat triangles close into a virus shell (with a net to print).
Also: CrowdedRoom, how long a small molecule takes to bump into its partner in a crowded cell (a toy model, ages 9 to 14).
Also: FlipTheScale, pick the instrument that can resolve each thing, from a hand to an atom.
Short, guided tours of the cells that build a body. Pick a cell, step through its parts one stop at a
time, and see what each piece does — written for middle- and high-school readers. Every tour cites
textbook-grade sources. Nothing is installed; nothing about you is collected.
Also: TenTimes, from a hand to an atom in steps of about ten.
Also: CellBudget, split a bacterium's protein budget and see how fast it grows (a toy model of a measured law).
This is the tool — the readable, shareable core. Explanations are Fold Commons editorial (CC BY 4.0); each tour
links to references such as Molecular Biology of the Cell on the NCBI Bookshelf and peer-reviewed reviews.
When a native version ships, it adds cell-scale visuals and offline use; it never gates the web.
≈3%a curated starter set of 6 of the ~200 human cell types, plus 2 non-human cells for contrast
A curated starter set of 6 of the ~200 broadly-recognized human cell types (plus two non-human model cells — a plant guard cell and E. coli — for contrast). The human body has on the order of 200 named cell types (and ~37 trillion cells); this edition tours a hand-picked teaching set, not the whole atlas.
What this set does not cover yet (5)
No sensory cells (photoreceptor rods/cones, hair cells of the inner ear, olfactory neurons).
No epithelial or secretory cells beyond the pancreatic beta cell (e.g. goblet, ciliated airway, keratinocyte).
No connective-tissue cells (fibroblast, chondrocyte, osteocyte, adipocyte).
No liver detoxification detail, kidney nephron cells, or germ-line stem cells.
Coverage is a teaching sample; it does not claim to represent every human cell type or every organelle.
System
Level
No tours match those filters.
AnimalStarter
Neuron — the body's wiring
Neuron (nerve cell) · Nervous system · 10–100 µm (soma); axons can reach over a metre
Walk a brain cell from the end that listens to the end that shouts.
1
Whole cell
The whole neuron
A neuron is a cell built for sending messages. It listens at one end and passes a signal out the other, sometimes over a very long distance.
2
Dendrites
Dendrites
These branching arms collect signals from thousands of neighbouring cells at junctions called synapses.
3
Nucleus
Nucleus and cell body
The cell body holds the nucleus, which stores the DNA and directs the proteins the neuron needs to work.
4
Axon
The axon
The axon is a long fibre that carries an electrical pulse away from the cell body. A fatty myelin coat lets the pulse jump along faster.
5
Axon terminals
Axon terminals
At the tip, the neuron releases chemical messengers called neurotransmitters to pass the signal to the next cell.
6
Mitochondria
Mitochondria
Firing and resetting takes a lot of energy, so mitochondria cluster where the work is heaviest to supply ATP.
Follow an immune cell that scans other cells and destroys the infected ones.
1
Whole cell
The whole cell
A T cell is a white blood cell of the adaptive immune system. Each one is born with a receptor of a single shape. When an infected cell shows a fragment that fits, that T cell is picked out and multiplies.
2
T-cell receptor
T-cell receptors
Receptors on the surface read short protein fragments that other cells display on MHC molecules, checking each cell for signs of infection.
3
Nucleus
Nucleus
A large nucleus fills most of the cell and holds the DNA that codes for its receptors and weapons.
4
Cytotoxic granules
Cytotoxic granules
When a target is confirmed infected, the T cell releases perforin and granzymes from these granules to trigger the target's self-destruct program.
5
Mitochondria
Mitochondria
Once activated, the cell rewires its metabolism and uses its mitochondria to power rapid division and the killing response.
Erythrocyte (red blood cell) · Circulatory system · 6–8 µm across, about 2 µm thick
See why the simplest human cell is shaped like a doughnut.
1
Whole cell
The whole cell
There are tens of trillions of red blood cells in your body. Their main job is carrying oxygen out to the body, and they also help carry carbon dioxide back to the lungs.
2
Cell membrane
Biconcave shape
The cell is shaped like a doughnut without a hole. That dished shape gives lots of surface for gas exchange and lets the cell bend to squeeze through the narrowest capillaries.
3
Cytoplasm (haemoglobin)
Haemoglobin
The inside is packed with the protein haemoglobin, which grabs oxygen in the lungs and lets it go in the tissues that need it.
4
Absent nucleus
No nucleus
A mature human red blood cell throws away its nucleus and most other organelles, freeing up room to carry more haemoglobin. The trade-off is that it cannot repair itself and lives only about 120 days.
Pancreatic islet beta cell · Endocrine system · about 10 µm
Learn how one cell measures your blood sugar and releases insulin.
1
Whole cell
The whole cell
Beta cells live in clusters called islets inside the pancreas. Their job is to keep blood sugar steady by releasing the hormone insulin.
2
Cell membrane
Sensing glucose
Glucose enters the cell and is broken down for energy. Rising energy closes channels in the membrane and makes the cell fire an electrical signal.
3
Rough endoplasmic reticulum
Rough endoplasmic reticulum
This is the factory floor where the insulin protein is first built and folded, studded with ribosomes that read the messenger RNA copied from the insulin gene.
4
Golgi apparatus
Golgi apparatus
The Golgi sorts and packages the folded protein into storage granules. As the granules mature, the protein is cut into its final form, insulin, ready to be released when blood sugar rises.
5
Secretory granules
Insulin granules
The calcium pulse from the electrical signal makes these granules fuse with the membrane and dump insulin into the blood.
Hepatocyte (liver cell) · Digestive system · 20–30 µm
Tour the busiest chemical factory in the body.
1
Whole cell
The whole cell
Hepatocytes do hundreds of jobs at once: storing sugar, making proteins for the blood, breaking down toxins, and clearing the pigment left over when old red blood cells are broken down.
2
Nucleus
Nucleus (often two)
Many hepatocytes carry two nuclei, or extra copies of their DNA. Why is still being worked out; one idea is that it helps the liver cope with damage and stress.
3
Smooth endoplasmic reticulum
Smooth endoplasmic reticulum
This network is the detox bench. Enzymes here chemically alter drugs, alcohol and waste so the body can get rid of them safely.
4
Mitochondria
Mitochondria
Hundreds of mitochondria per cell power all this chemistry and help process fats and amino acids.
5
Glycogen granules
Glycogen stores
The cell stockpiles spare sugar as glycogen and releases it between meals to keep your blood sugar from dropping.
Watch two bean-shaped cells open and close a pore so a plant can breathe.
1
Whole cell
The whole cell
Guard cells come in pairs on the underside of a leaf. Together they open or close a tiny pore called a stoma to let gases in and out.
2
Cell wall
A reinforced cell wall
When the pair swell with water, their walls stop them simply getting fatter: they lengthen and bow apart into a curve, opening the pore between them. Textbooks long credited a thicker inner wall; experiments now show the stiff ends of the pair matter too.
3
Vacuole
Vacuole
Water rushing into this large central sac makes the cell firm and puffed up, forcing the stoma open.
4
Chloroplast
Chloroplasts
Unusually for the leaf surface, guard cells contain chloroplasts, which capture sunlight and help signal when the pore should open.
5
Nucleus
Nucleus
The nucleus holds the genes for the sensors and pumps that respond to light, carbon dioxide and water — signals that together set when the pore opens and closes.
Escherichia coli (bacterium) · Bacterium (prokaryote) · 1–2 µm long
Compare a bacterium with your own cells and see what it does without.
1
Whole cell
The whole cell
E. coli is a bacterium that lives in the gut. It is far simpler than any human cell — no nucleus and no membrane-wrapped organelles.
2
Cell wall and membranes
Cell envelope
A tough peptidoglycan wall sits between two membranes, giving the rod its shape and protecting it from bursting.
3
Nucleoid
Nucleoid
The DNA is a single circular chromosome that floats free in a region called the nucleoid — there is no nucleus to enclose it.
4
Ribosomes
Ribosomes
Thousands of ribosomes read messenger RNA copied from the DNA and build proteins. Many antibiotics work by jamming the bacterial ribosome.
5
Flagella
Flagella
Several whip-like flagella spin together as a bundle, like a propeller, to swim. When they reverse, the bundle flies apart and the cell tumbles to a new direction — runs and tumbles that carry it toward food and away from danger.
Curated teaching sample, not an atlas. These are 8 hand-picked cell types chosen to
span animal, plant and bacterial cells — roughly 3% of the ~200 named human cell types. The
coverage gauge above is deliberately honest: it will never claim to be complete.
Simplified on purpose. Explanations are written for a general and school-age audience. They
leave out exceptions and fine detail; follow the per-tour sources for the full picture.
Non-spatial by design. This edition is a DOM/text reader. It does not attempt cell-scale
3D — that stays in the native app. No Mol*, no WebGL, no external data fetch.
No servers, no tracking. Every tour is baked into this page at build time. The only stored
state is your filter/step choices in the page URL, so a link is shareable.
Editorial, then sourced. The plain-language text is Fold Commons editorial (CC BY 4.0); the
biology is anchored to the cited textbook and review sources on each card.