The National Institute of Mental Health (or NIMH for short) is a medical institution that focuses on finding cures for major illnesses. Mostly psychological ones, hence the name. They serve as the secondary antagonists of the Secret of NIMH.
The Secret of NIMHEdit
It is revealed by Nicodemus (or his diary, rather) that NIMH was the place Jonathan, himself and the others escaped cruel animal tests that they saw as torture. NIMH itself is not really seen, just the cages in which the animals are kept in. The only other part of the building that is shown are the ventilation ducts in which the majority of mice die. In the climax of the film, Farmer Fitzgibbons calls NIMH to poison the Rose Bush and exterminate the rat colony within. NIMH arrive the next morning, but by then the Rats have started their journey to Thorn Valley and Mrs. Brisby's home has been successfully moved.
The Secret of NIMH 2: Timmy To The RescueEdit