Nina investigates why people have to sleep, with the help of her five sense neurons.

Experimenters Kirsty, Olim and Tegan visit Nina in her lab. They find out that babies and children need more sleep than grown-ups because sleep is really important in helping their brilliant bodies to grow. Next, they visit a post office and see the postman sorting the letters so they won't get lost. Nina explains that when people sleep, their brains sort out all of the information they have taken in from their senses during the day. It is thought that this helps us to remember things later on.

Back at the lab, the children play with some very lively toys. They see that when the toys' batteries run out, they stop moving. Nina recharges the batteries so that the toys can be full of energy again. She explains that people run out of energy too at the end of a long day. So they need to get plenty of sleep to give their brilliant bodies time to recharge. Show less