To grow a crystal, you need a supersaturated solution of the desired material. To make this solution, the material must be dissolved in a solvent, such as water, until no more can be dissolved. The solution is then heated to encourage further dissolution and then cooled slowly while stirring until the material precipitates out in the form of crystals. Depending on the material, the solution may need to be seeded with a seed crystal or nucleation site to encourage the formation of the crystals. The solution can then be left to cool and the crystals will continue to grow until they reach the desired size.