In order to specify plankton organisms of about 10 to 500 µm size one needs to look through the microscope. This type of analys is is one of the three taxonomic methods we use along with flowcytometry and phytoplankton pigment analysis by means of HPLC (High Performance Liquid Chromatograpy). We mainly use inverted microscopes which are also good for quantitative analysis of the Phyto- or Microzooplankton in water samples. Some of the microscopes are equipped with a UV-excitation lamp, suitable objectives and filters, to perform fluorescence microscopy, which could be very helpful e.g. to distinguish between heterotrophic and autotrophic organisms. A connected camera with monitor is a good tool for teaching and outreach activities.