From a tiny cell to a whole body
Your body is built from tiny pieces too small to see with your eyes alone. They are called cells. Let's look at real ones under a microscope first, then zoom inside a cell, and then zoom out one step at a time until we can see a whole body.
Drag the picture inside the circle to move the slide around, just like sliding the stage of a real microscope. The coloured band on each objective lens is the colour code used on microscopes all over the world.
What is a cell, and how small is it?
A cell is the smallest thing that is alive. Think of it as one LEGO brick. Every living thing is built from cells. Some living things are just one cell, like bacteria and amoebas, but your body has about 37 trillion cells.
Who named it a "cell"?
In 1665 an English scientist called Robert Hooke sliced cork very thin and looked at it through a microscope he built himself. He saw tiny boxes packed side by side, which reminded him of the small rooms monks lived in, so he chose the word cell meaning a small room.
The 3 rules of cells
1. Every living thing is made of cells.
2. The cell is the basic unit of life.
3. New cells only come from old cells dividing.
Scientists call these rules cell theory.
The shrinking ruler
Slide right to shrink one step at a timeColour key: ■ eyes · ■ magnifying glass · ■ school microscope · ■ electron microscope
Inside an animal cell: a whole tiny city
Inside every cell are organelles, tiny organs that each have their own job, like a city with a town hall, power stations, factories and a post office. Tap any part, then try switching to Cell City mode.
Inside a plant cell: a city with walls and a solar farm
A plant cell has almost everything an animal cell has, plus 3 special extras: a cell wall that makes it strong, chloroplasts that make food from sunlight, and a large vacuole that stores water and holds the plant upright.
Plant cells vs animal cells: what is different?
Here are the two cells side by side. Press Show only the differences and the shared parts fade, leaving only what belongs to one kind of cell.
Sorting game: which cell does this belong to?
Tap a label, then tap the box you think it belongs in
| Feature | Plant cell | Animal cell |
|---|---|---|
| Shape | Boxy and fixed, because of the cell wall | Round or irregular, and bendy |
| Cell wall | Yes, strong | No, only a cell membrane |
| Chloroplasts | Yes, makes its own food from light | No, has to eat food |
| Vacuole | One big one in the middle | Small, several, or none |
| Centrioles | No | Yes, they help when the cell divides |
How do cells work? Try the experiments yourself
Cells never sit still. They take in water, make food, burn energy and divide all the time. This lab has 4 experiments. Try them all to earn the Lab Scientist badge.
The doubling game
One cell splits into two, two into four, and on and onGuess first: how many rounds until you have as many cells as your body?
Every kind of cell looks different
Your body has more than 200 kinds of cells, and each kind has a shape that suits its job, just as the tools in a toolbox look different because they do different jobs. Try matching each cell to its job.
White blood cell on the hunt
Tap anywhere inside the box to release a germ. White blood cells can change shape: they stretch part of themselves around a germ, swallow it, and break it down.
Zoom out: from one cell to a whole living thing
Cells of the same kind group together into a tissue. Different tissues join to form an organ. Organs that work together make an organ system, and all the systems together make you. Press the next step and watch it zoom out.
Your body has 4 kinds of tissue
Epithelial tissue
Cells packed side by side in sheets, covering the outside of the body and lining the inside of organs, like skin and the wall of the gut.
Connective tissue
Holds parts together and supports them: bone, tendons and fat. Did you know? Blood counts as this kind of tissue too.
Muscle tissue
Can contract, so you can move, your heart can beat and food can travel along your gut.
Nervous tissue
Sends electrical signals all over the body. It is found in the brain, spinal cord and nerves.
Your body: the biggest team ever
Every cell you have met ends up working as part of a team in the 11 organ systems. Each system has its own star cell.
Keep exploring the body layer by layer
Bones, muscles, lungs, heart, kidneys, eyes, ears and brain, with lots more experiments to try
Test yourself and collect every badge
You earn each badge by finishing the activity in a chapter. Badges are saved on this device, so you can come back and carry on.
14 questions
Fancy a game on this lesson?
Every question from this lesson is in the Body 101 arena. Race the clock, duel someone at home, play as a team, beat the bosses, or practise with no timer at all.