The visual diversity of crystals

Crystals are solid materials that form a regular lattice (or framework). The form of the lattice is determined by the molecular structure of the substance. Crystals emerge when a transition between phases occur, e.g. a solution of a substance in water precipitates when the water evaporates. Another scenario is when a substance is heated until it melts and thereafter cools down. Macroscopic visible crystals are table salt, snowflakes and diamonds. Under magnification using a microscope crystals show an almost endless variety of shapes, lines, bended forms and repeated intricate patterns, often in a fractal manner.
Due to their 3 dimensional special geometry, crystals demonstrate remarkable optic characteristics, such as  their
refractive indices (frequency dependent bending of light) and birefringence (double refraction). This exceptional optical behavior can be demonstrated using polarized light. By rotating one polarizing filter in the light beam of the microscope a whole gamut of different colors can be evoked. All photos on this website are homemade using dozens different substances ranging from melted urea till precipitated sugar.