Where would Earth science be without zircon? Tiny crystals of zircon occur in many rocks, and because their atomic structure remains stable over very long periods of geological time, they are able to provide a picture of the early history of the Earth and of the evolution of the crust and mantle. Zircon has long been recognized as the best geochronometer using the radioactive decay of uranium to lead. Recent developments in analytical techniques, using small-diameter laser, ion and electron beams, high-precision mass spectrometry and a variety of microscopic imaging methods, allow us to obtain the ages of tiny volumes of complex crystals that record stages in their long growth history. Coupled measurements of the isotopes of oxygen and hafnium provide a mineralogical window into the separation of the Earth's crust from the mantle and the temperature and character of processes involved in crustal evolution. Zircon is being used to unravel ever more complex geological systems, presenting exciting opportunities for research on this remarkable mineral.