Zhe Liu

Water in a stream doesn't flow in a uniform sheet; it carves winding paths where the current runs faster. Electrons in a Hall thruster, a device that pushes a spacecraft with a jet of plasma, behave much the same way. Inside the thruster, a magnetic field confines electrons, which ionize the gas and produce thrust.

Light is a stream of photons. In a special waveguide, resembling a narrow corridor, a 'gatekeeper' atom usually lets them through one at a time. This phenomenon is the domain of single-particle spectroscopy.