Which fundamental force keeps atomic nuclei from flying apart?

Atomic nuclei contain protons that all repel one another electrically, yet nuclei remain stable because the strong nuclear force acts as a powerful short-range binding force. This force operates between quarks inside protons and neutrons, and as a residual effect between nucleons in the nucleus. Its range is only about a femtometre, but within that range it is strong enough to bind helium, carbon, iron, and many heavier nuclei. Without it, matter as we know it would not exist.