Everything in our universe, from the tiniest water drop to the largest mammal, is made of the same constituent: the atom. This discovery didn’t fulfill the curiosity of your ancestors; rather, it motivated them to explore its inner structure. And deep there, at the core of matter, they found the electrons: elementary, negatively charged particles that stabilize matter by balancing the positive nuclei.

In the 20th century, the familiar view of the atom as a nucleus with orbiting electrons became obsolete, when electrons revealed their mysterious wave-like nature...