刨根问底
páo​gēn​wèn​dǐ

to get to the bottom of something

  1. 刨 páo
    to dig
    To dig, excavate, or unearth something from the ground.
  2. 根 gēn noun
    root (botany, family)
    the root of a plant; the part that grows underground to absorb nutrients; also refers to a child who carries on a family line
  3. 问 問 wèn verb
    to ask
    to ask; to inquire; to request an answer from someone
  4. 底 dǐ adverb
    ins and outs
    The truth behind a matter; the underlying details or background information