The initial configuration for simulating Checkerboard, Cell Sorting and Engulfment patterns. It consists of about 1,000 active cells surrounded by an extracellular medium. The active cells are randomly located in the unit sphere, and their types are randomly sampled from M. Cells of type τ1 are colored in black while cells of type τ2 are colored in grey. One hundred cells of type τ
were uniformely placed on the frontier of the unit disc.