Complex fluids like polymer solutions, melts etc. are characterized by relaxation motions at widely varying length and time scales, ranging over several orders of magnitudes. My research aims at a multi-scale analysis of the dynamics occurring at different length scales and their interplay with any imposed flow on the system. For this, I employ computational techniques like molecular dynamics (which provides information at the level of atoms and molecules) and Brownian dynamics ("Mesoscale" simulations that probe the behavior of groups of atoms, molecules). Using the fundamental information obtained from such simulations, we can, in principle, try to build constitutive models for such systems, which can be used with CFD to understand the non-newtonian effects produced by these complex fluids in flow.