来龙去脉 (lái lóng qù mài)

lit. the rise and fall of the terrain (idiom); fig. the whole sequence

Character breakdown

来 (lái) · 7 strokes

Simplified form of 來. Pictograph of a stalk of wheat. The current meaning "come" is a phonetic loan. The original meaning "wheat" is now written as 麥.
龙 (Lóng) · 5 strokes

Pictograph of a dragon curled up. The simplified character 龙 was adapted from the cursive form of the traditional character 龍.
去 (qù) · 5 strokes

Depicts opening the mouth (口) wide (大) to let a yawn leave the mouth. Original form of 呿.
脉 (mài) · 9 strokes

Simplified form and variant of 脈. The blood vessels is the part of the body (⺼) where blood flows (永).

Usage

请把这件事的来龙去脉说清楚。
the rise and fall of the terrain (idiom); (fig.) the whole sequence of events; causes and effects
qǐng bǎ zhè jiàn shì de lái lóng qù mài shuō qīng chǔ 。