The fact that nature is an excellent chemist is demonstrated by the abundance of molecules, so-called natural products, which it produces biosynthetically. These natural products are also of central importance to us humans. They are used in many ways in our everyday lives, especially as active agents in medicine and agriculture. Prominent examples are antibiotics such as penicilins isolated from molds, the anti-cancer drug Taxol from the Pacific yew tree, and pyrethrins found in chrysanthemums, which are used to combat pest infestations.