Puppy Development From 1 to 8 Weeks. Physical Development. At around 12 weeks, puppies gain better control of their bladders and bowels. They may start to sleep through the night without accidents.

In puppy kindergarten, the Duke team followed the development of 101 puppies, tested every two weeks between eight and 20 weeks old. All were Labrador retrievers or Labrador-Golden retriever mixes.