Book excerpt: The Blue-Green Algae attempts to assemble a unified picture of blue-green algae as living organisms. It describes the organism's general features of form and structure, cellular organization, cell biology, gas vacuoles, and movements. The book addresses the culture, nutrition, growth, photosynthesis, chemosynthesis, heterotrophy, respiration, nitrogen metabolism, differentiation, reproduction, and life cycles of the blue-green algae. The organisms' freshwater and terrestrial ecology, pathogens, symbiosis, evolution, and phylogeny are also explained. These organisms form a substantial fraction of the biomass in several important types of habitat. Consequently, it is desirable to understand their activities if natural resources are to be conserved and used to best advantage. This book will be useful to students and research workers in this field of interest.