Well-dispersed Y2O3:Eu nanocrystals, with a size less than 10 nm, and self-assembled nanodisks (see Figure) could be synthesized by a simple organometallic route. Two strong emission peaks located between 610 and 630 nm, and a 2.6 % quantum yield, are achievable upon excitation at 330 nm. Excellent dispersibility, a long lifetime, and improved emission may allow Y2O3:Eu nanocrystals to be useful for biological labeling.