升堂入室

shēngtángrùshì
  1. lit. to reach the main room and enter the chamber (idiom)
  2. fig. to gradually attain proficiency
  3. to attain a higher level

CEDICT

语本《论语．先进》：「由也升堂矣，未入于室也。」比喻学问或技艺循序渐进，达到高深的境界。《三国志．卷一一．魏书．管宁传》：「娱心黄老，游志六艺，升堂入室，究其阃奥。」也作「登堂入室」、「入室升堂」。

重編國語辭典

Entry Composition

1 升堂 shēngtáng
  1. (historical, of the court official) to commence court proceedings
  2. to commence court proceedings
2 入室 rùshì
  1. (figurative) to gain mastery of
  2. (literal) to enter someone's house or room
  3. to enter someone's house or room
  4. to gain mastery of