Squirrels start off their lives with no hair at all except for small hairs around their noses for feeling things, like a cats whiskers. They are so small you can hold them in your hand.
When the baby squirrel gets older, it starts to grow its fur and grows bigger.
As the squirrel grows its body fully develops like ours do. They get all of their fur and grow their teeth.
Sometimes a squirrel gets a disease that makes them turn all black.