A
crystal is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions.
Crystal growth is a major stage of a
crystallization process, and consists in the addition of new
atoms,
ions, or
polymer strings into the characteristic arrangement of a crystalline
Bravais lattice. The growth typically follows an initial stage of either homogeneous or heterogeneous (surface catalyzed)
nucleation, unless a "seed" crystal, purposely added to start the growth, was already present.