Nitty-gritty (noun)

1. The essential, fundamental or basic details of a matter.
2. The crucial or most important aspects of something.
3. The core or heart of a situation.

Origin:

Uncertain; perhaps from dialectal british nit and grit meaning 'the essential elements', or from african american english enid and grit, a corruption of the phrase 'in the grits and in the gravy', meaning 'in the thick of it'.

Examples:

1. Before we can make a decision, we need to get down to the nitty-gritty of the problem.
2. The nitty-gritty of the contract negotiations were hashed out over several long meetings.
3. We need to understand the nitty-gritty of the issue before we can move forward with any solutions.