The development of microfluidic systems has grown rapidly over the past decade, generating a number of applications, some of them already turned into commercial products. In such systems, unusual lengthscales are involved (typically from 1 to 100 microns) and several new scientific questions arise. In particular, physical phenomena, negligible in flows of conventional sizes, may play an important role in microflows. Interface phenomena are especially important owing to the large values reached, in miniaturized systems, by the surface/volume ratio. Interface dynamics in microsystems, is a recent subject, interesting in its own right, and valuable to explore in view of controlling heat or mass transfer in microfluidic systems. At the moment, research studies currently investigate effects due to the coupling between microflows and geometry, wall slip, surface roughness, electrokinetics, variable fluid properties and conduction/convection. A substantial part of the research effort attempts to explore new fundamental processes, disantangling, in some case, their complex nature, along with exploring exciting new applications.