Highly charged ions in cold confines High-energy irradiation can strip many electrons away from individual atoms, producing ions with charges of +10 or more. However, many of the interesting properties of such highly charged ions are hard to study or exploit under the extreme conditions needed to prepare them. Schmöger et al. cooled down argon ions with +13 charges from the megakelvin temperatures needed for their generation to millikelvin temperatures appropriate for high-precision spectroscopy. The method relies on sympathetic cooling by a cold sample of singly charged beryllium ions and is likely to be applicable to a broad range of other elements. Science , this issue p. 1233