Between three to six months, your kitten will be growing and developing strong muscles, bones and social skills. They need an energy-dense food as they have three times the energy requirement of adult cats, but their milk teeth have yet to be replaced by adult teeth so it needs to be easy for them to eat—rehydrating kibble in hot water or milk works well. They'll be sleeping like an adult cat, for 13 to 16 hours each day. Some breeds of cats can show the abilities and signs of being able to reproduce from as young as four months, so be aware of this and talk with your vet about your options.
The final stages of your kitten becoming a cat
After six months, your kitten will have become a cat. In their "junior" stage they will be playful and fully socialized, although it's important to maintain good behavior through clear feeding patterns. After two years old, they are categorized as in their "prime," and this often is when they are at their most healthy with a glossy coat, a strong skeleton and muscles, and excellent hunting reflexes.
Understanding the process by which your kitten develops into an adult cat means you'll be able to give them the right support they need in their diet, behavior, and home life. If you have any concerns that your kitten isn't progressing in the right way, consult your vet.