"When I started reading about it, it just got more and more interesting," says Libbrecht. Despite studying them for so long, he is still not sure exactly how these crystals form.

He has experimented by creating different formations. For instance, growing the crystals at varying temperatures dramatically changes their appearance.

A crystal is created as water vapour in air freezes, so the molecules that are forming a crystal all move around as they do so.

Somehow, the energy that binds the crystals together is related to how much heat is present when they are created.

That is why they all look so different. As water turns to ice in the sky, the temperature fluctuates as it falls. No two crystals will follow exactly the same path, therefore they all look just a little bit different.

This results in some of these beautiful formations. Anybody who lives in a cold climate can see them. The stellar dendrites for instance, occur when the temperature is about -15 °C.

You can see more of Libbrecht's photos on his website