Four fundamental forces control every kind of interaction observed in nature, and strong force is the most powerful of these. Sometimes strong force is called “strong nuclear force” because it exercises all its strength within an atom’s nucleus.
From an atom’s perspective, strong force is a hundred times stronger than electromagnetism and trillions of times stronger than gravity. It’s strong enough to hold atoms together, keeping everything around you from flying apart.
If you had a window into an atom and could see the invisible force working, strong force would be in there pulling protons and neutrons together. That’s quite a feat because protons are bad roommates. Positively charged particles repel each other, just like two positive poles of a magnet. Strong force makes these protons share a cramped space. Zoom in further, inside the protons and neutrons, and you’ll find quarks. Strong force is inside the protons and neutrons holding all the quarks together.