Macroplastics are the most visible part of pollution, and the largest in mass. Mostly derived from the fragmentation of macroplastics, micro- (1μm-5mm) and nanoplastics (< 1 μm) are more significant in number, and present a greater danger to human and environmental health. Micro- and nanoplastics are emitted throughout the lifetime of plastics, not just when they become waste. The distribution of plastics in the environment is highly heterogeneous. Studies often focus on accumulation sites rather than on diffuse pollution, which has a major impact. In environmental samples, analyses can characterize polymers, but generally not additives, which represent thousands of potentially toxic molecules that are impossible to identify in complex matrices. Analysis of micro- and nanoplastics in biological tissues, to understand their impact on organisms, is still under development.