Living things are made from different atoms and molecules.

Below is the periodic table of elements. It shows all of the possible types of atoms known to exist in the universe.

Highlighted in red are the 6 most common atoms (building blocks) found in living things on Earth.

• The carbon (C) element is found in most molecules within living things.
• It is for this reason that we describe all living things on Earth as being “carbon-based”.
• In theory, we might find living things that do not consume carbon-based molecules and therefore are not carbon-based.
• Instead, they could make use of other atoms that have similar properties to carbon (highlighted in blue on the periodic table).
• Examples include silicon (Si; commonly found in sand) and germanium (Ge).