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. Dr. Alexandra Kraberg has worked with phytoplankton for over 12 years, including time as a phytoplankton analyst for long-term monitoring programmes in Ireland and the UK. After receiving her PhD from the University of Liverpool in 2002, she moved to the Alfred Wegener Institute for Polar and Marine Science, where she has worked on a range of phytoplankton projects, e. g., dealing with intraspecific diversity in diatoms. Since 2004 she is the co-ordinator of the international PLANKTON*NET database system (http://planktonnet.awi.de). She is also a member of the ICES working group on phytoplankton and microbial ecology. Dr. ClausDieter Dürselen received his PhD from the University of Oldenburg in 1995. While at Oldenburg as a post doc, Dr. Dürselen worked as a phytoplankton expert in different national and international research projects. Together with a former research colleague, he founded the environmental company AquaEcology in 2002. Dr. Dürselen is a plankton consultant to the regional and local water authorities of Northern Germany. Prof. Dr. Marcus Baumann has studied phytoplankton of the North Sea and the polar regions, both the Arctic and the Antarctic for more than 30 years. After two years as a researcher at the Alfred Wegener Institute he became head of the environmental services department at the FH Aachen, University of Applied Sciences, before receiving a professorship in biotechnology. Currently he is the rector at the FH Aachen.