Not too sticky There is increasing evidence for a role of liquid-liquid phase separation (LLPS) in many cellular processes. Many proteins that undergo LLPS include prionlike domains (PLDs), which are enriched in polar amino acids and often interspersed with aromatic residues. Combining experimental data with simulations, Martin et al. quantified concentrations of PLDs in coexisting dilute and dense phases as a function of temperature and show that the phase behavior is determined by the number of aromatic residues and their patterning, with uniform patterning of aromatic residues promoting LLPS and inhibiting aggregation. They developed a sticker-and-spacers model that can predict the phase behavior of PLDs on the basis of their sequence. Science , this issue p. 694