Grinding barley is a necessary step in making tsam pa, one of Tibet's most important dishes.  Barley flour is ground by hand on a millstone. Throughout the grinding process, white flakes of barley tend to fall from the millstone, creating a white, flaky mess which covers the area.  These falling barley flakes are here compared to snow: another common sight in the region.  Snow and barley are similar in color as well as their tendency to fall.  The primary difference between the two is said here to be human involvement.  While the creation of barley flour requires human labor, snow is created naturally, without human involvement.