Domesticated rats and mice are very different from their wild counterparts.
Rats and mice are most often thought of as pests, rather than pets, and when they do live in a home, it's usually against the owner's will. What many people don't know is that the types of rats and mice that can be kept as pets are quite different from common rats or wild mice. Domesticated rats and mice are naturally tame, curious, friendly, and sometimes even shy, with simple requirements that make them easy to care for.
If you decide to adopt a rat or mouse, pet expert Marc Morrone recommends housing it in a large fish tank with a secure locking cover. Line the bottom of the tank with Aspen bark bedding (pine or cedar wood shavings can cause skin rashes) or a paper pulp such as Care Fresh, and wash the tank out with soap and water once a week.
As for diet, combine a commercially prepared rodent food with regular servings of fresh fruit and vegetables, and be sure to provide a constant supply of clean water. Avoid picking up your rat or mouse by its tail; instead, cup the animal in your hands, or scoop it up with a coffee cup.