Gravitational lensing lets scientists find and map invisible dark matter in the universe.

Most of the stuff in our universe is completely invisible. We call it dark matter. It does not shine or block light, so we cannot see it directly. But it still has weight, which means it pulls on space and bends light. By looking at how background galaxies are stretched and twisted, scientists can work backward to map out where this invisible matter is hiding. It is like seeing water drops on a window by watching how the view behind them changes.