A representative example of the formation of CsCl-like crystals can be seen in Extended Data Movie 1. Here, nucleation occurs from within these blobs, often starting from the surface where interfacial fluctuations more easily allow for transient changes in density. For lower interaction strengths, particles can rearrange resulting in blobs that are spherical to minimize surface tension, but for higher interaction strengths we also observe more dendridic gel structures, which then crystallize through nucleation within the dense phase, followed by propagation as in Fig. . Absorption of neighboring blobs is common, especially at higher density where many small blobs nucleate initially. For some of these cases, we tracked the particles in the blob being absorbed and found that the vast majority of those in the final crystal arrived via direct flow rather than through evaporation from the blob then subsequent deposition.