In this book, each phytoplankton species is featured with its own description, and most are illustrated with micrographs using LM. Scanning electron microscopy (SEM) is also used but only for a very limited number of samples. For some organisms that are difficult to be identified to the species level using LM, they are described at the genus level. The classification used in this book is in accordance with taxonomic books such as by Hoppenrath et al. (2009), Tomas (1997), Allen and Cupp (1935), and Jensen and Moestrup (1998). It is hoped that the information provided in this book will be helpful in the understanding and identification of diatom and dinoflagellate species.