Microplastics, or plastic fragments smaller than 5 mm in diameter, are widespread water contaminants globally, raising international alarm due to their persistence, mobility, and toxicity. Microplastics enter into aquatic systems from primary (microbeads and plastic pellets) and secondary (fragmentation of larger plastics) sources through runoff, wastewater effluent, and atmospheric transport. Having invaded the environment, they are conveyed by flows and lodged in sediments or in food webs. The present review integrates recent findings concerning their mode of behavior within the environment, their biological consequences, and health implications for mankind. Microplastics are transportation media for unwanted chemicals—persistent organic pollutants and heavy metals—thatexaggerate their effects in the environment. Microplastics are widely ingested by aquatic life forms, precipitating obstructive disorder in the gut, dwarfing growth, inflammation, and trophic transfer. Human exposure is increasingly documented through seafood consumption, drinking water, and inhalation, though the long-term effects are largely uncharacterized. There is no international standardization of existing monitoring techniques, and thus comparative analysis and regulation are problematic. This review delineates the essential research requirements and calls for interdisciplinary collaboration, improved analytical tools, and policy changes. Mitigation of microplastic pollution is no longer an option—it is a requirement to safeguard ecosystem resilience and public health against a silent but increasing environmental hazard.