The use of substances derived from plants, fungi, bacteria and marine organisms has a long tradition in medicine. Together with their derivatives, and synthetic compounds deduced from natural product precursors, they represent a major part of today's pharmaceutical market. In molecular biological research, natural products also play an important role as tool compounds in pathway screening and validation of target identification concepts. They provide innovative opportunities in drug discovery, leading to a detailed understanding of biological pathways and revealing the functions of involved enzymes or receptors. This book highlights the biodiversity-driven approaches which are now of eminent importance in natural products research. It addresses the question why natural products display such a complex chemical information, what makes them often unique and what their characteristics are. Practical questions such as supply of natural substances and production optimization strategies are also covered.