Iron is the main ingredient in various forms of iron and steel, but the various types of metals contain other elements as well. Sometimes these elements are unwanted; other times they're ...

Everything we can see and touch, and quite a lot that we can’t as well, is made of tiny particles called atoms. Some substances, like particles of this iron, contain only one kind of atom.

Earth’s core could contain helium from the early solar system. The noble gas tucks into gaps in iron crystals under high pressure and temperature.