the most basic and important facts of something.
We didn't actually get down to the nitty-gritty (= start to talk about the most important facts) until half way through the meeting.
英语词组固定搭配大全包含18674条英汉双解词组,基本涵盖了全部常用英文词组、短语的翻译及用法,是英语学习的有利工具。