All books of heterocyclic chemistry - with only perhaps one recent book - describe only synthesized heterocycles but ignore dealing with those made by nature. This book provides a balanced, concise and informative account in the way life started and why nature selected to synthesize heterocycles, not only as a source of energy but also as reagents that affect a multitude of biological transformations. The text provides an up-to-date survey of the various types of heterocycles and describes their synthesis via classical tools as well as biosynthesis. This text also focuses on the application of heterocycles in the chemical industry as dyes, pigments, pharmaceuticals, agrochemicals and catalysis. A brief chapter to apply the principles of green chemistry in the area of biologically relevant heterocycles are described. This book provides a unique overview of the subjects and is ideal for undergraduate and graduate students in organic chemistry as well as pharmaceutical and medicinal chemistry.