打破沙锅问到底 [- - shā ɡuō wèn dào dǐ]insist on getting to the bottom of the matter; be inquisitive; get to the bottom of sth.; inquire into the bottom facts in [of] this affair; interrogate persistently; probe sth. to the bottom; wish to know every detail of sth.：
•¶ 小明老爱问为什么， 老爱打破沙锅问到底。 Xiaoming always asks why and he'll never be satisfied until he knows everything.