追本穷源
zhuī​běn​qióng​yuán

to get to the root of the matter

  1. 追 zhuī verbnoun
    to investigate
    to look into; to investigate; to get to the bottom of a matter; to trace
  2. 本 běn proper nounadverb
    origin
    the source, foundation, or fundamental part of something
  3. 穷 窮 qióng
    thoroughly
    thoroughly; exhaustively; to investigate something to its very roots
  4. 源 yuán noun
    origin
    (bound form) root; origin; the starting cause or basis of something