Molecules store energy and, as bonds are formed and broken, every chemical process can either store or release energy as well. This talk will discuss practical ways for incorporating this common knowledge into reaction design and in searching for new physical phenomena. I will discuss how much energy can one store in common functional groups, introduce the familiar textbook functionalities that accumulate more energy than an excited state, and will introduce the phenomenon of electron upconversion, a counterintuitive way to transform weak reductants into strong reductants in a thermodynamically favorable fashion. Such processes enable photoredox and electrocatalytic transformations where a single electron can drive multiple catalytic cycles.