Coastal phytoplankton boasts an incredible diversity of life forms. It is not rare to find 40 or 50 different species in just a few drops of water. In this “Photo Guide for Northern European Seas” we describe the major phytoplankton groups, diatoms and dinoflagellates with additional information on ciliates and smaller flagellates. In total we provide taxonomic, ecological and biogeographic information on more than 130 taxa. As the majority of students and professional plankton analysts will mainly work with the light microscope, the species in the book are documented with light micrographs, giving the reader a realistic view of species as seen in a water sample. The book is, therefore, not only suited for students and environmental managers, but also for amateur microscopists and laypersons.