Microbeads are tiny plastic particles, typically less than 5 mm in diameter, used in various products like cosmetics, toothpastes, and abrasive cleaners. When washed down drains, they enter wastewater systems but are often too small to be filtered out. They are then released into rivers, lakes, and oceans. Once in aquatic environments, microbeads persist for a very long time and pose a significant threat to marine life.