Crystallization is usually referred to as the bottleneck of X-ray crystallography. A sparse matrix incomplete factorial screen of precipitating
conditions typically produces many different types of protein aggregation and precipitation, among them large single crystals. If the protein or
precipitant concentrations are too high one can see brown matter with no distinct shape and size (amorphous precipitation). When the solution is
undersaturated, the drop will often be completely clear and devoid of any kind of precipitation. Figure 3 shows several examples for precipitation
phenomena and crystals (Dessau et al., 2006). More precipitation phenomena with more detailed interpretation can be found at