Nina investigates why people have skin, with the help of Felix, her touch neuron. Experimenters Ciaran, Harry and Jordan visit Nina in her lab and find out that skin is like a rucksack for the body, keeping the insides safe and in place.
Then they visit a car wash and discover that skin is also good at keeping things out of bodies, such as dirt and germs. And skin is waterproof too, which is a good thing when you have a bath!
Back in the lab, they use their magnifying glasses to see that people have lots of tiny hairs in their skin. Nina explains that when people are cold, the tiny hairs stand up, helping to trap warm air and warm them up. Skin also helps to cool people down when they are too hot by making them sweat.