Tim de Jongh

The law discovered by Wolfgang Pauli forbids identical particles from occupying the same spot. Hence, in cold matter, a Fermi sea is born: particles, like water, fill energy levels from bottom to top. The shape of the sea's surface — including 'islands' of emptiness — dictates the properties of the whole system.

A light field, like a neat waffle iron, presses a regular pattern of bright and dark regions into space. Atoms get stuck in the brightest spots as if in tiny dimples: that's an optical lattice. It's a favorite tool for physicists who want to study quantum behavior of matter in its pure form.