nitty-gritty nitty-gritty /ˈnɪtiˈɡrɪti/

noun

1. The choicest or most essential or most vital part of some idea or experience  ( centre [Canadian, British] , gist , heart and soul , inwardness , kernel , marrow , meat , nitty-gritty , nub , center [American] , core , essence , heart , pith , substance , sum )
   the choicest or most essential or most vital part of some idea or experience
    The gist of the prosecutor's argument
   the gist of the prosecutor's argument
    The heart and soul of the Republican Party
   the heart and soul of the Republican Party
    The nub of the story
   the nub of the story