This book explores the fascinating world of microbial polyunsaturated fatty acids (PUFAs), highlighting their natural diversity, biosynthetic pathways, and industrial potential. It begins by explaining the biological importance of omega-3 and omega-6 fatty acids, followed by an in-depth review of PUFA-producing microorganisms including algae, fungi, bacteria, and yeasts. The book then delves into the genetic and metabolic engineering strategies used to enhance PUFA production, as well as the optimization of fermentation and culture conditions. Practical aspects of downstream processing-such as extraction and purification-are also addressed. Furthermore, the book examines the various applications of microbial PUFAs in nutrition, pharmaceuticals, cosmetics, and lab-grown meat. Finally, it discusses sustainability, market trends, and future directions. This comprehensive resource is ideal for researchers, students, and industry professionals interested in microbial biotechnology and functional lipids.