The bottom half is a mathematical summary of crystallographic reflection groups; here, "group" has a specific meaning in mathematics: it measures how symmetrical something is. So, objects which are more symmetrical have "bigger" groups associated with them. The groups for crystalline structures generated by finitely many reflections have a particularly neat method of classification by the chalk diagrams, which are called Dynkin diagrams. The top half represents crystals, using the randomness of poured paint on canvas to mimick the growth pattern of dendrites. By tipping the rigid canvas, every point on its surface experiences the same forces due to gravity, and so all the drips move in near-parallel courses. Drips that haven't completely dried are also slightly affected by tipping and shaking the canvas, and so the amount of de-correlation between the crystals can be controlled in both their spacial and temporal separation.