Fungal natural products are friends and foes of humans such as deleterious mycotoxins, cytotoxic, carcinogenic compounds or beneficial compounds such as antibiotics, fungicides, insecticides, antiviral and antitumor metabolites. Understanding fungal diversity and estimation of fungal species on our planet poses a great challenge to researchers. This complexity is further multiplied by secondary metabolite diversity of fungi, which requires interdisciplinary studies. It is extremely important to understand the fungal secondary metabolism to stop human, animal and plant diseases caused by fungi and harvest their valuable metabolites. Furthermore, many secondary metabolite gene clusters are silenced under laboratory conditions. It is vital to develop effective methods to activate those clusters in order to discover novel potent metabolites. This e-book is a compilation of original review articles contributed by leading fungal secondary metabolite researchers with a wide range of expertise. Important aspects of fungal secondary metabolism, including regulation, genome mining, evolution, synthetic biology and novel methods have been discussed. This book will be a great source to those people, who are interested in understanding overall structure, diversity and regulation of production of these tiny but precious chemicals.