Background <p>Microplastics (MPs) and nanoplastics (NPs) are plastic fragments generated through the degradation of plastic products in the environment. These fragments accumulate in microorganisms, plants and animals, posing critical threats to ecosystems. Fluorescence imaging techniques are widely used to quantify the accumulation and distribution of MPs and NPs in biological samples, providing insights into their fate and potential toxicity.</p> Purpose of review <p>This review presents a comprehensive overview of fluorescence imaging techniques for visualizing MPs and NPs in biological samples, focusing on the fluorescent dyes used for staining MPs and NPs, the intrinsic autofluorescence properties of plastics enabling direct detection without staining, and various fluorescence microscopy techniques.</p> Recent findings <p>Recent studies demonstrated the feasibility of label-free fluorescence imaging of MPs and NPs utilizing their intrinsic autofluorescence, with or without fluorescence enhancement. Super-resolution fluorescence microscopy has been successfully applied to visualize NPs as small as 50 nm in a whole animal.</p> Conclusion <p>Fluorescence imaging techniques are powerful tools for visualizing MPs and NPs in biological samples, offering valuable insights into their interactions within living organisms. This review underscores advancements in fluorescent dyes for staining MPs and NPs, intrinsic autofluorescence properties of MPs and NPs, and fluorescence imaging methodologies, highlighting their pivotal contributions to advancing research on MPs and NPs.</p>