There are millions of different substances in the world because these elements can combine in a vast number of ways to form compounds. For example, carbon, hydrogen, and oxygen can combine to form a variety of different compounds, including water, carbon dioxide, and sugar. These compounds, in turn, can combine with other elements to form even more complex substances.

In addition, many elements can exist in different forms called allotropes. For example, carbon can exist as graphite, diamond, and fullerene. These allotropes have different physical and chemical properties, which can lead to even more diversity in the substances that can be formed.

Finally, the interactions between molecules and atoms can also lead to the formation of new substances. For example, when water molecules interact with carbon dioxide, they can form carbonic acid. This reaction is responsible for the bubbles in carbonated beverages.