What is an electron? A seemingly trivial question addressed to a physicist might, at best, generate an embarrassed smile and, at worst, a complex and lengthy explanation, probably almost incomprehensible to most. This question is also certainly not irrelevant to a chemist since the electron governs the reactions that form molecules. Probably from school physics notions, the most common representation of the electron is that of an electrically charged, very small spherical object, of a negative charge, to be precise, revolving like a planet around its sun, represented by the atomic nucleus made of protons and neutrons. This image is somehow representative of Bohr’s atomic model. It is reassuring but quite far from the electron model to which contemporary physics has arrived. Indeed, the planetary model of the electron imagined as a small sphere revolving around its sun, that is, the atomic nucleus, has an immediate analogy with the solar system. The electrons are the planets, and the sun is the atomic nucleus. The earth’s orbit around the sun, however, is not circular but elliptical, so one might wonder whether the electron around the nucleus will also assume an eccentric orbit. As we will find out, the answer to the question of electron orbits will take us very far.