The elementary spark that makes matter stable, lost as matter decays around it.
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...
Does it have a size? What is spin?
Beyond electrons orbiting the nuclei.