Scientists aren't exactly sure why play behavior develops in kittens. Many of them believe that young animals play to improve their co-ordination and prepare themselves for adult life, like most sophisticated species do. Young lions, for example, will chase their tails or other moving objects to develop their predatory skills.
You can spend hours playing with kittens. They seem to have boundless energy for chasing balls and strings, jumping straight up in the air, and zooming all over your home. Their enthusiasm for playing is contagious; we love to play with them.
Even when your cat is grown up, she will still have a lot of fun -- and gain health and emotional benefit from -- playing with you.