Babies are required to have more sleep then most adults. The smaller the baby the more sleep they need.
Babies just eat and sleep. Every time they are sleeping they are growing more and more. Young children do not need much sleep like babies but has to have more then adults.
Grown ups also need sleep for a period of time. While they are sleeping cells that are warn gets replaced. After their sleep time they must get up for work the next day.
Adults need food for energy because they are not growing any more. While young children and babies have food for energy, muscles and bones.Young children need energy to run they start running at the years 1-2.