见微知著jiàn wēi zhī zhù

看到微小的苗头，就知道可能会发生显著的变化。比喻小中见大。

例故圣人见微知著，睹始知终。——汉·袁康《越绝书》

英from one small clue one can see what is coming; from the first small beginnings one can see how things will develop;