The structures of all crystals can be classified according to the symmetry of the unit cells. There are in total 7 groups, collectively called Crystal Systems: Tricinic, Monoclinic, Orthorhombic, Tetragonal, Trigonal, Hexagonal, and Cubic. The symmetry of each group is described by the relationship between the lattice sides a, b, and c and angles α, β and γ. Click on a crystal system to get started.