Crystals are particular kinds of solids that are made from a regular arrangement, or lattice, of atoms. Most rocks and metals are crystals, so are snowflakes and salt.
Most crystals have regular, geometrical shapes with smooth faces and sharp corners.
Most crystals grow in dense masses, as in metals. Some crystals grow separately, like grains of sugar.
Some crystals are shiny and clear to look at. Crystals got their name from the chunks of quartz that the ancient Greeks called krystallos. They believed the chunks were unmeltable ice.
Crystals form by a process called crystallization. As liquid evaporates or molten solids cool, the chemicals dissolved in them solidify.
Crystals grow gradually as more and more atoms attach themselves to the lattice, just as icicles grow as water freezes onto them.
The smallest crystals are microscopically small. Occasionally crystals of a mineral such as beryl may grow to the size of telegraph poles.
A liquid crystal is a crystal that can flow like a liquid but has a regular pattern of atoms.
A liquid crystal may change color or go dark when the alignment of its atoms is disrupted by electricity or heat. Liquid crystal displays (LCDs) use a tiny electric current to make crystals affect light.
X-ray crystallography uses x-rays to study the structure of atoms in a crystal. This is how we know the structure of many important life substances such as DNA.