Vitamin B5 (Pantothenic acid), polarised light micrograph. Pantothenic acid in a molten viscous state with trapped air bubbles. Turbulence from heating causes variations in the density which we can see as changes in colour. Bubbles behave like tiny lenses, focusing the light from beyond. As the viscous 'gloop' cooled, it contracted and cracked under the compression. Magnification: x70 when printed at 10cm wide.