Microscopic observations of the inhabitants in aquatic environments reveal the complex array of organisms that are woven together into a tapestry that is informative, ornate, colorful, and artistic. The diversity of life, especially among the photosynthetic organisms called algae, displays a unique suite of patterns and structures that allows the names to be assigned. This book compiles microphotographs from many groups and hundreds of genera to illustrate the beauty of algae and assist in their identification. The images in this guide were initially started as an academic, hands-on teaching guide rather than a digital version. This first edition organizes and arrays the images in taxonomic groups that can be used to instruct a new generation of phycologists, those that study algae. The identification and classification of algae from Linnaeus in 1767, through the 19th and 20th centuries, mostly relied on pen and ink line drawings, carefully constructed to illustrate morphological features that separated species, and these are still a valuable resource. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) brought significantly higher resolution than light microscopy, illustrating the external and internal structures through black and white imagery. As digital photography improved for the light microscope in the past several years, color images of the key features that distinguish one organism from another can be generated.