Plastic pollution is a major issue, as much for its potential impact on human health as on ecosystems and the environment. Microplastics, non-biodegradable and persistent, are a new global pollution that must be characterized on all size scales, from the nanometer to the millimeter, in order to control and limit the risks of exposure for humans and to allow the implementation of clean-up strategies. There is currently no standard methodology for the identification and characterization of nanoplastics and microplastics smaller than 10 µm in solution. The aim of this internship is to develop a multi-instrument methodology dedicated to the analysis of these sub-micrometer scale objects.