牽一髮而動全身

1. • lit. pulling a single hair makes the whole body move (idiom)
2. • fig. a small change in one part can affect the whole system

Character by character

• 牽(qiān)lead along
• 一(yī)one
• 髮(fà)hair
• 而(ér)and
• 動(dòng)move
• 全(quán)surname Quan
• 身(shēn)body