The Rats of NIMH is a trilogy of children's books, the first one by Robert C. O'Brien, and the second and third by his daughter Jane Leslie Conly. They tell the story of a society of rats rendered intelligent by scientific experimentation.
The books are:
In 1982, Mrs. Frisby and the Rats of NIMH became the basis for the animated film The Secret of NIMH, directed by Don Bluth. In 1998, a film sequel to The Secret of NIMH, called The Secret of NIMH 2: Timmy to the Rescue was released. The sequel has no connection to Jane Leslie Conly's sequel, Racso and the Rats of NIMH, but did have a connection with Mrs. Frisby (the story about the six missing mice). It is recently announced that a live-action/animated reboot is in development.