Surface-tension-confined microfluidics (STCM) has become a rapidly emerging research area. STCM utilizes surface tension (i.e. energy) to control movement of streams or droplets of liquid. Thus, STCM typically operates on a 2D platform rather than in 3D. This evolution of microfulidics from 3D to 2D platforms opens new opportunities in applications as well as the physical chemistry of surfaces, as reviewed by H. Lee et al. on p. 471.