Garnet is among the most studied—and most beloved—minerals, owing to its commonality in diverse geologic contexts, its often large euhedral crystals, its sometimes dazzling colors, and its propensity for preserving information about its growth history. Chemically zoned garnet represents a remarkable tool for deciphering metamorphic conditions and the evolving tectonic processes that drive garnet growth over many millions of years. In the deep Earth, garnet is a key rock-forming mineral, influencing the physical properties of the mantle and the composition of mantle-derived magmas. Garnet has been sought for ages as a semiprecious gemstone (the birthstone of January) and has been mined or synthesized (including nonsilicate garnet) for industrial purposes, including laser, magnetic, and ion-conductor technology. This issue of Elements will emphasize the most recent innovations in thermodynamic, geochemical, geochronologic, and industrial applications of garnet, while providing perspective on decades of garnet-related research.