After giving birth, a

32-year-old woman notices that her newborn son has tiny hairs on his back. As

she has never seen anything like this on other children before, she asks the

doctor what it is. The doctor explains that these are the tiny hairs that a

fetus has on most of its body before birth and that they usually disappear before

birth. Sometimes they can remain after birth, but they disappear within days or

weeks at most. What do we call these tiny, fine, light-coloured hairs?