A new precursor library yields high-quality quantum dots for device applications Also see Report by Hendricks et al. Colloidal semiconductor nanocrystals (NCs) or “quantum dots” offer exquisite control of absorption and emission colors for device applications by tuning their size and shape ( 1 ). The proliferation of NC applications has been enabled by the “hot-injection” synthesis, which can tightly control the particle size to achieve pure colors ( 2 ). However, current hot-injection synthesis recipes are largely incompatible with low-cost, large-area remote phosphor applications of NCs. Reagents are too expensive, reaction mixtures too dilute, and conversion yields too low, especially if size tuning is accomplished by adjusting the reaction time. On page 1226 of this issue, Hendricks et al. ( 3 ) report on a radical improvement of the hot-injection synthesis economics of metal sulfide NCs by introducing a library of inexpensive thioureas as reagents.