Trichome

Trichomes are structures on a plant's leaves. They look like tiny hairs sticking out from the surface of the leaf.
Trichomes are made of living cells, which can look very different. Some trichomes have one long cell. Other trichomes are a long chain of cells. They may have branches which make them look like a star. 
Trichomes help to shade the leaf from the sun. They block too much wind from moving across the leaf surface. This stops too much water from leaving the leaf. Animals might not eat leaves with trichomes because they do not like the taste.
Glandular trichomes have chemicals in them. They break when the leaf is touched, and then the chemicals come out.