A drop of coffee on a tabletop often leaves a dark ring behind. This everyday mark is a reminder that a drying droplet is not passive: As water evaporates, it can transport the particles suspended inside it toward the edge. Scientists call this the coffee-ring effect.
Source: [Phys.org](https://phys.org/news/2026-09-spider-webs-mosaics-nanosheets-graphene.html)