Liquid flows on the microscale often do not behave as we would expect intuitively from our macroscopic point of view. The goal of this course is to provide an insight into specific fluidic phenomena that appear on the scale of typical lab-on-a-chip devices. The course intends to give a more theoretical introduction of fundamental formulas and equations. Nevertheless a range of selected devices/applications will be shown to exemplify specific microfluidic properties. Using the Navier-Stokes equation we will first derive solutions for some basic microfluidic situations, with specific focus on pressure-driven flows. The impact of liquid/channel wall interfaces (capillary forces) on the solution transport in microchannels will be discussed. Analysing the convection-diffusion equation will allow to understand issues related to diffusion and mixing encountered in many lab-on-a-chip applications. In the last part of the course the physical background of liquid transport by electrical fields on the micro- and nanoscale will be explained in detail (electroosmosis). We will also derive the formulas governing the manipulation of cells or particles by electric (dielectrophoresis) and magnetic forces in microfluidic devices.