Hydrogen is an element. An element is a substance that cannot be broken down into a simpler substance by any known means. Each of the 92 naturally occurring elements is therefore one of the fundamental materials from which everything in the Universe is made.

Hydrogen (chemical symbol H), named after the Greek word for “water-forming”, is the most abundant element in the Universe. In fact more than nine-tenths of all atoms are hydrogen atoms.

It is the stuff of stars, of cold “empty” space and of the Earth. Hydrogen is found everywhere and in most compounds. It is the most universal element.

Hydrogen is also the simplest element in existence. As a result, hydrogen is a tiny atom. But its simplicity explains why it is so universal: it is the building block from which other elements are made.

Although it is so universal, hydrogen is rarely found as a gas on Earth. It makes up only three-quarters of 1% of the mass of the planet. This is because hydrogen molecules (combinations of two hydrogen atoms, described by the symbol H2) weigh so little that they can escape from the Earth’s atmosphere. The only free hydrogen that survives is in pockets deep underground, part of the decay process that also forms oil and natural gas.

Hydrogen is a gas that easily catches fire and can be explosive. Yet it is made in huge quantities each year. About half of it is used to make ammonia, which is the basis for many fertilisers. About one-third of the hydrogen produced is used in refining metals. Another main use of hydrogen is to make a liquid called methanol, one of the starting materials in making artificial fibres.