i Register
In some senses, nitty-gritty is marked as colloquial. Watch for register when choosing this word.
noun
The core or essence of something; the gist.
He gave a short summary without getting into the nitty-gritty of the problem.
adj
Dealing with something in great depth.
1976, United States. National Commission on Arthritis and Related Musculoskeletal Diseases, Arthritis - Out of the Maze We deal with them at a very, very nitty gritty level, and we deal with the results of years and years of problems that they've had in the past.