Each experiment is performed in an Insall chamber. The chamber is loaded with 2uM caffeine/ development buffer. In each case, cells are developed on 1% agar / development buffer until the onset of streaming (looks like a Voronoi diagram beginning to form). At this point, cells are harvested and placed onto a glass cover slip, which is then inverted and placed on the chamber. The outer well is drained, and replaced with the appropriate attractant-containing medium (as detailed for each experiment in the paper).