Microplastic particles floating in water. Small particles of plastic like this have been found in huge quantities in marine environments, where they pose a serious threat to marine life and ecosystems. Such small particles typically form from the breakdown of larger plastic objects, such as bottles and bags, that have been improperly disposed of and made their way into the sea. They are swept up by ocean currents and concentrated in gyres, the most famous being the Great Pacific Garbage Patch. It is estimated that this area of the ocean contains up to two trillion particles with a mass approaching 100, 000 tonnes, over an area of nearly two million square kilometres. Despite its dramatic name, it is not evident to the naked eye, as most of the particles are tiny.