Lanthanide luminescent materials have gradually become indispensable in a wealth of applications, including phosphors for lighting and displays, security inks and tags, lasers, optical fibers, night vision, photocatalysis, bioprobes, nanoscopy, and light-activated drug delivery. In this short review, we describe the basic properties of lanthanide luminescence, highlight major current applications, and discuss the growing trend of embedding luminescent lanthanide ions into nanostructures, which not only enhances their emissive properties but also, and quite importantly, unlocks a whole (nano)world of new applications.