Everything you can think of is made up of tiny particles called atoms, they are so small it is almost impossible to imagine, but they are the building blocks of everything – the ground, the sky, mobile phones, animals and plants, even you and me.

These atoms tend to stick together in groups called molecules and these make the substances we can recognise like water or plastic or make up the air we breathe.

Because molecules are made up of more than one atom, they can be arranged in different shapes and the shapes can be important and useful to us.

Amazingly there are both right-handed and left-handed molecules. This is where two molecules are exact mirror-images of each other. What’s more some molecules can change shape from left to right-handed.

All living things, like animals and plants are made up of lots of different types of molecules, but some of the most important ones are called amino acids. Amino acids are pretty special and can help us with dating.

In living things, animals and plants, most amino acids are left handed molecules. When that plant or animal dies, then these left-handed molecules start changing to right-handed ones.

Scientists have found out how quickly this happens and can also measure how many left-handed molecules there are compared to right-handed ones. Knowing all this, they can work out how long ago that living thing died.

This is a technique used by archaeologists and ice age scientists to work out how old their finds are. It works best on shells, corals, eggshells and teeth, so if an archaeological site has any of these materials in it, we can date them and find out how old the site could be.