穷根问底
qióng​gēn​wèn​dǐ

get to the bottom of things

  1. 穷根 窮根 qióng​gēn
    to get to the bottom of things
    To investigate or probe deeply into the origin of a matter; bound form typically occurring in 穷根究底 qióng​gēn​jiū​dǐ or 穷根探源 qióng​gēn​tàn​yuán
  2. 问 問 wèn verb
    to ask
    to ask; to inquire; to request an answer from someone
  3. 底 dǐ adverb
    ins and outs
    The truth behind a matter; the underlying details or background information