Colloids—mixtures of particles made from one substance, dispersed in another substance—crop up in numerous areas of everyday life, including cosmetics, food and dyes, and form important systems within our bodies. Understanding the behavior of colloids therefore has wide-ranging implications, yet investigating the rotation of spherical particles has been challenging. Now, an international team including researchers from The University of Tokyo Institute of Industrial Science has created particles with an off-center core or "eye" that can be tracked using microscopy. Their findings are published in Physical Review X.