Animals and plants are built from cells, and both kinds are eukaryotic: their DNA sits inside a nucleus. They share the same core machinery: a cell membrane around the outside, mitochondria that make ATP, ribosomes that build proteins, the endoplasmic reticulum (ER) and the Golgi apparatus. A few structures are not shared. Turn both cells around in 3D, tap a structure to read what it does and how big it really is, and compare. Keep an eye on the scale bar: a typical animal cell is about 20 µm across (a fiftieth of a millimetre), a nucleus about 6 µm, a mitochondrion 1–2 µm and a ribosome only about 25 nm.