In recent decades, rare earths have become vital to a wealth of advanced materials and technologies including catalysts, alloys, magnets, optics and lasers, rechargeable hydride batteries, electronics, economical lighting, wind- and solar-energy conversion, bio-analyses and imaging. In this perspective article we give a broad overview of rare earth resources and uses first and then of selected applications in dedicated fields such as telecommunications, lasers, photovoltaics (solar-energy conversion), lighting (fluorescent lamps and OLEDs), luminescent probes for bio-analyses and bio-imaging, as well as magnetism and magnetic refrigeration. © 2011 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.