This book describes current understandings and recent progress in four areas: in the first one, the cytochalasans, a group of fungal derived natural products characterized by a perhydro-isoindolone core fused with a macrocyclic ring are shown to exhibit high structural diversity and a broad spectrum of bioactivities. The second one is dedicated to a description of bioactive compounds from the medicinal plants of Myanmar, the third one is dedicated to new structure elucidation techniques in the field of sesquiterpenes. The last one discusses the endogenous natural products that are produced by human cells including endogenous amines, steroids, and fatty acid derived natural products. The co-metabolism and natural product production of the human microbiome is also described including tryptophan, bile acids, choline, and cysteine.