Since the 50s of the last Millennium the world production of plastics has increased massively and led to a continuous increase in the amount of plastic waste in the world's oceans. The plastic material is biologically inert, hardly subject to mineralization and fragmented in the environment. Plastic particles are continuously becoming smaller and more frequent (microplastics; MP). How the waste gets into the sea, how it is detected and discovered by researchers and what consequences it can have for living organisms are topics of an education program on marine litter implemented in the AWI school lab OPENSEA. We focus on independent hands-on experiments which are framed by several modules. The detection of marine litter as components of the current modules at the school lab. Our aim is to impart scientific knowledge and awareness through experimental work. We have implemented experiments to sample plastic waste of different size classes in the environment and characterize the plastic material (microscope, infrared spectrometry). Our new module is based on the fluorescent dye Nile red aiming to visualize microplastic particles in environmental samples. It offers a research-oriented approach and an independent research access applying a new, cost effective, and harmless method for testing and staining with Nile red dye for school labs. Environmental samples and defined plastic polymers are stained with Nile red to examine the polymer in more detail. When excited with blue light, the dye bound to the polymer emits in the yellow-red range. The fluorescent colour of the plastic piece depends on the chemical structure of the respective polymer. Depending on this method, learning modules and experiments for students were developed, and evaluated in the OPENSEA school lab. In addition to working materials for students and teachers, we provide background material, on the long run this module will be available online.