In this online biology textbook, learn about atoms and molecules as they relate to life. Find out about topics such as electrons and energy, chemical bonding, and chemical reactions.

Learn how basic elements form molecules to support life.

Atoms are very, very small. Atoms are so small that it is often said that there are as many atoms in a single grain of sand as there are grains of sand on all of the world's beaches - certainly a difficult thing to prove, but you get the...