Lice are tiny little insects, with little claws on their legs so they can cling onto their host.
Because lice need the heat and blood of a host to survive; they are parasites.
Some lice live permanently on birds or mammals; they hang onto their feathers or fur.
But there’s another type of louse that only lives in people’s hair!
The lice in our hair must have had an ancestor that lived millions of years ago, on the first anthropoids, or great apes.