Crystals - nature putting itself in order
Crystals are ordered structures of molecules or atoms. Normally a substance can exist in three different phases: solid, liquid and gas. Take water for example. The solid is ice, the liquid is water and the gas is vapor. Which phase a substance is in depends on the temperature and the pressure. Water freezes to ice at zero degrees Celsius and boils at one hundred centigrades at normal air-pressure. If the pressure is lower the boiling temperature goes down and the other way around. (Not all materials form crystals in the solid phase, there are also so called amorphous materials which do not have an ordered structure.)
At the same time as there are many different solids they also have very different structures. Especially spectacular are the patterns formed by water molecules in a snowflake. Other substances, as for example carbon, can exist in no less than three different crystalline forms, whereas the pure metals have simple patterns with "infinite" extension.
Applications based on discoveries in condensed matter physics is an important part of our every day life. This applies for example to the computer you are sitting in front of, which would not work without semiconductor technology. The early work in the field which led to the development of the transistor gave its inventor the 1956 Nobel Prize in physics. Other important discoveries are amongst others superconductivity and liquid crystals.