nitty-gritty vs heart and soul

nitty-gritty and heart and soul both are nouns.

Word	Noun	Adjective	Verb	Adverb
nitty-gritty	Yes	No	No	No
heart and soul	Yes	No	No	Yes

As nouns, nitty-gritty and heart and soul are synonyms defined as:

nitty-gritty and heart and soul: the choicest or most essential or most vital part of some idea or experience

Other synonyms of nitty-gritty include center, centre, core, essence, gist, heart, inwardness, kernel, marrow, meat, nub, pith, substance, sum.

nitty-gritty (noun)	heart and soul (noun)
the choicest or most essential or most vital part of some idea or experience	the choicest or most essential or most vital part of some idea or experience

nitty-gritty (adverb)	heart and soul (adverb)
	with complete faith