Crystals are formed from dissolved substances or when molten substances cool slowly. As the solutions evaporate and the materials cool, their atoms come closer, forming a crystal.
The crystal gradually grows as the process continues. Some crystals grow into beautiful shapes with bright colours. In these crystals, atoms are arranged in regular patterns.
Below Crystals info from Wikipedia (Read More):-
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification.
The word crystal is derived from the ancient Greek word κρ?σταλλο? (krustallos), which had the same meaning, but according to the ancient understanding of crystal. At root it means anything congealed by freezing, such as ice.[1] The word once referred particularly to quartz, or "rock crystal".
Most metals encountered in everyday life are polycrystals. Crystals are often symmetrically intergrown to form crystal twins.
http://en.wikipedia.org/wiki/Crystals
