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.
[1] They tell the story of a society of rats rendered intelligent by scientific experimentation.
In 1998, a sequel to the film called The Secret of NIMH 2: Timmy to the Rescue was released.
The sequel has no connection to Racso and the Rats of NIMH and was met with poor reception.
A live-action/animated remake was reported to be in development; James Madigan was attached to direct.