Since it was originally proposed in a rudimentary form by Thomas and Fermi in the 1920s, given a firm theoretical footing with theorems by Hohenberg and Kohn in the 1960s, and experienced explosive growth in popularity beginning in the 1990s, Density-Functional Theory (DFT) has been shown to be a highly impactful method for studying electronic structure. Through the calculation of the total energy and its derivatives, the properties of atomic, molecular, and condensed-phase systems can be quantified at an affordable computational cost (N 3 scaling) with near chemical accuracy in many cases. Some properties that are not feasible to measure experimentally can be obtained through DFT simulations-from societal imperatives such as the mechanistic description of inhibition reactions of prospective COVID-19 antiviral drugs to more theoretical curiosities like the relative thermodynamics of silicates at the extreme temperatures and pressures of the Jovian core. Furthermore, the 1998 Nobel prize was awarded to Walter for his leading contributions to DFT and John Pople for computational methods in quantum chemistry, which include many practical tools used in modern DFT codes.. Indeed, the publications reporting the workhorse exchangecorrelation functionals of molecular and materials chemistry, B3LYP and PBE, have, as of the time of this writing, 110,000 and 170,000 citations or thereabouts, respectively, ranking them among the most cited scientific papers. Despite the accolades and prevalence of DFT, it would be a mistake to interpret a citation to a functional as understanding of the approximations thereof on the part of the user.