Researchers have developed a simple test strip that makes invisible nanoplastics visible under a basic microscope. Nanoplastic particles made visible: the newly developed test strip from the University of Stuttgart allows dangerous nanoplastic particles to be detected under a light microscope. The researcher's test strip is an easy-to-use tool that provides a solution for their analysis. The technology could serve as a mobile test strip that would provide information on the content of nanoplastics in water or soil directly on site. (2025) Optical sieve for nanoplastic detection, sizing and counting.