Over the past two decades, the development trajectory of micro- and nanoplastics (MNPs) research has been complex, with scattered focuses. A systematic review of global research trends is essential to clarify historical developments, identify key hotspots, and highlight emerging frontiers. To this end, we employed a thematic progression strategy combined with co-citation and keyword clustering networks to systematically map research hotspots and trace global progress on MNPs over the past five decades. A total of 12,851 related publications were extracted. Overall, the development of MNPs research demonstrates significant phases, diversity, and complexity, covering multiple dimensions including sources, environmental distribution, toxicological effects, tracing mechanisms, and management strategies. The research trajectory of MNPs clearly reveals a full-chain research path, from source identification and migration-diffusion to environmental interaction behaviors, highlighting the multi-media coupling propagation mechanisms and the potential risks of complex ecological disruptions. Studies on the distribution of MNPs in environmental media have evolved from early marine pollution concerns to a more integrated research field that covers water-soil-air media, multi-scale, and multi-morphological pollution behaviors, exhibiting high interdisciplinary and evolutionary features. Research on the toxicological effects of MNPs has evolved from "ecological biological responses" to "molecular mechanism identification" and then to "human health risks," establishing a complete logical chain in toxicity understanding from macro to micro and from experimental studies to real-world exposure. These findings provide a foundation for understanding the environmental fate and multi-dimensional harm mechanisms of MNPs, offering references for institutions and researchers in future research directions.
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