Andalites gave 5 humans the power to morph! Meet Ax, an Andilite, and the Animorphs, Tobias, Rachel, Marco, Cassie, and (Prince*) Jake.
*Jake isn't a prince. That's just what Ax calls him.
Ax is an Andalite, Tabias is a human traped in the body of a red-tailed hawk, and the rest are human. Now here's the bad thing about being able to be able to morph--if you don't morph back into your natural form in two hours, your stuck forever. That is what happened to Tobias.