AbstractAny kind of device or machine requires a substrate, energy, and information signals. If we wish to operate at the nanometer scale, we must use molecules as substrates. Energy‐ and signal‐processing at a molecular level relies on cause/effect relationships between the input supplied and the kind of process obtained. We have classified energy‐ and signal‐processing at the molecular level according to the nature of the input (electronic, photonic, or chemical) and the nature of the obtained effect (electronic, photonic, or chemical process that follows). By coupling the three kinds of inputs with the three types of resulting processes, nine types of molecular‐based processes (electronic, photonic, chemionic, electrophotonic, electrochemionic, photoelectronic, photochemionic, chemiophotonic, and chemioelectronic) can be identified. In this concept article, looking at molecular transformations in an unconventional way, we have tried to give a flavor of some of the new features that project the old science of chemistry towards novel achievements.