Soft materials such as colloidal suspensions, emulsions, foams and gels often display complex and unusual behaviors compared with ordinary solids or liquids. From a mechanical point of view, for instance, they can resist deformation like solids, but they can also start to flow like liquids when a sufficiently strong external drive is applied. This transition from solid-like to liquid-like behavior, known as "yielding," is central to the physics of soft amorphous materials and to many industrial and biological processes.

Soft materials such as colloidal suspensions, emulsions, foams and gels often display complex and unusual behaviors compared with ordinary solids or liquids. From a mechanical point of view, for instance, they can resist deformation like solids, but they can also start to flow like liquids when a sufficiently strong external drive is applied. This transition from solid-like to liquid-like behavior, known as "yielding," is central to the physics of soft amorphous materials and to many industrial and biological processes.

Basic biology courses teach that cells contain organelles—such as the nucleus, mitochondria and Golgi apparatus—set apart by lipid membranes to get things done. Recent cell biology research has revealed another organizational principle at work in cells across all orders of biology.