Abstract: Micro and nano scale fluid systems can behave very differently from their macro scale counterparts. While this provides a new technological opportunity to create devices and structures with remarkable performance, simulation for design at these scales requires special treatment of molecular effects that is beyond the scope of conventional continuum-fluid modelling. In this talk I will describe the hybrid molecular/continuum techniques we are constructing to tackle these types of multiscale flow problems. I will discuss domain-decomposition vs heterogeneous techniques, and sequential vs concurrent methods. I will show that time-scale separation can be exploited in some physical situations in order to obtain satisfactory accuracy at much less computational expenses. To illustrate the different approaches, I will present examples of engineering applications, including water transport in energy-efficient nanotube membranes, and unsteady flows in converging/diverging nano channels.