Four-week-old kittens have fully developed senses of sight, smell, and hearing, but they are still very uncoordinated. Their teeth are starting to come in, so when you play with your four-week-old kittens, make sure you don’t play nibbling-on-the-human games, or they might become a habit (and poke tiny holes in your person!)
By the time our kittens reach four weeks, they are doing everything an adult cat does:
Kittens this age are excited to nom kitten kibble, but they still need their mommy’s milk to grow and thrive. If you are hand-rearing kittens, keep bottle feeding them for a couple more weeks to supplement the kitten kibble. Don’t give kittens adult cat food, cow milk or other dairy products, or bread or other carbohydrate-rich foods. Kittens can eat tinned food, but kitten kibble is probably best.
If your kittens are starting to explore the house, you need to kitten-proof: make sure cables and cords are wrapped up and out of reach. Put plants on high shelves. Make sure garbage cans have tops that close. Kittens love to climb, so if your decorations might be dangers, you should consider putting them away until you have re-homed the kittens (or they stop scaling your shelving units like little fluffy mountaineers!)
Although the kittens are exploring all the nuances of catting, they still need their mommy! She teaches them how to cat professionally.
For the next several weeks, you should spend as much time with your kittens as possible, and invite lots of people over to play with them. This is the age to socialize your kittens so they will grow up to be friendly pets. If you have other animals living in your house, they can be introduced to the kittens now. Also, tiny children and the elderly.