A few points: * you might expect raindrops themselves to be quasi-random since they are formed by accumulation of humidity in small areas * the surface tensio

A few points: * you might expect raindrops themselves to be quasi-random since they are formed by accumulation of humidity in small areas * the surface tension of the drops would certainly help in accumulating nearby drops in the table mesh, but not enough by itself to combine nearby cells (which you can see with several examples in the picture) * I suspect the filled-cells are formed by condensation along the wire mesh instead of drops falling directly into each hole, and since the condensation would be evenly distributed (the air around the table will have uniform humidity), you would expect the filled cells to be regularly distributed like this since a drop forming in a cell would use condensation required by neighbors to form drops