An array of images that illustrates the crystallization phase space of CypA. Concentrated solutions of CypA were mixed in a 1:1 volume ratio with solutions of PEG 3350 at varying concentrations. The labels on the axes indicate the final concentrations after mixing. CypA crystallizes readily in PEG 3350 solutions; however, the crystal size and morphology varies dramatically as a function of protein and PEG concentration. Specifically, at low CypA and low PEG 3350 concentrations (bottom left corner) the crystals that form are few and large, while at high PEG 3350 concentrations (right side) CypA aggregates and no crystals form. In the middle of the phase space, dense solutions of small crystals form.