Cleopatra's nose; a small thing with a huge influence
A set phrase referring to the idea that a tiny detail (like the shape of Cleopatra's nose) can change history or have an enormous impact. Often used in discussions of historical contingency or the butterfly effect.
When discussing historical what-ifs, Cleopatra's nose is often brought up.
If Cleopatra's nose had been a little lower, world history might have been different.
From the French philosopher Blaise Pascal's pensée: 'Le nez de Cléopâtre: s'il eût été plus court, toute la face de la terre aurait changé.' The phrase entered Japanese as a set expression.