Polyethylene accounts for nearly one-third of the world's plastic waste. An interdisciplinary team has now investigated the progressive degradation of polyethylene in the environment for the first time. Although the degradation process leads to fragmentation into ever smaller particles, isolated nanoplastic particles are rarely found in the environment. The reason is that such decay products do not like to remain on their own, but rather attach rapidly to larger colloidal systems that occur naturally in the environment.