The boundary layer flow is an important phenomena in the field of fluid dynamics. The flow consists of two categories of fluids i) Newtonian ii) non-Newtonian or complex fluids. In this research the focus has been given to the study of boundary layer flow over a stretching/shrinking surface. Further, the boundary layer flow is divided into two sections related to finite and infinite domain. The finite domain of the boundary layer is known as thin film. The viscosity and thermal conductivity have been considered constant as well as variable or temperature dependent respectively. The steady and unsteady fluid flows have been assumed over a stretching sheet/cylinder. The complex fluids have been considering single and three fluid combined. In chapter one we discussed the basic concepts of fluid mechanics, different types of the fluids, fundamental equations, some non-dimensional parameters, the basic Williamson fluid model, Maxwell fluid model, Jeffrey fluid model, Walter’s-B viscoelastic fluid and the basic idea of Homotopy Analysis Method in detail. In chapter two we displayed the literature review of the concerned research. In chapter three we considered the effect of thermal radiations on a thin film of Williamson fluid over an unsteady stretching surface with variable properties of viscosity and thermal conductivity. The effect of thermal radiations and viscous dissipation terms are involved in the energy equation. The energy and concentration fields are also discussed with the Soret and Dufour effects. The effects of non-dimensional physical parameters like thermal conductivity, Schmidt number, Williamson parameter, Brinkman number, radiation parameter and Prandtl number have been discussed In chapter four we investigated the unsteady motion of Williamson Nano-fluid on a stretching sheet. The effect of thermal conductivity on temperature has also been considered. The governing equations are presented under the Dufour and Soret approximations. In order to understand the physical presentation of the embedded parameters such as Dofour number Du , Schmidt number Sc , Soret number Sr , the Brinkman Number Br , Williamson number and Radiation parameter R are graphically plotted and discussed. In chapter five we considered the mass and heat, transportation of Williamson fluid with variable viscosity and thermal conductivity over an unsteady shrinking and stretching surface. The shear stresses and thermal radiation field are also encountered in the time dependent energy equation. The model, employed for Williamson fluid, contains the Dufour and Soret effects. Study mainly focused to understand the physical appearance of the embedded parameters based on the characteristic length of the liquid flow. The obtained results are drafted graphically and discussed. In chapter six we considered the appearance of the boundary layer flow for non-Newtonian Walter’s B fluid over the surface of an unstable cylinder. The Dufour and Soret effects with heat and mass transfer have been faced in the flow. The effects of the involved physical parameters of the problem like Reynolds number, Walter’s B fluid parameter, Prandtl number, Schmidt number, Dufour and Soret numbers have been illustrated. The behavior of Skin friction, local Nusselt number and Sherwood number have been described numerically for the dynamic constraints of the problem. In the last chapter, we examined the features of liquid film non-Newtonian Nano-fluids under the influence of thermophoresis. For this exploration, we projected a model for Jeffrey, Maxwell and Oldroyd-B Nano-fluids concluded unstable stretched surface in the existence of an oblique magnetic field and also the thermal conductivity is measured directly related to the temperature whereas the viscosity invented inversely related to the temperature. Inserting the thermophoretic nanoparticles efficiently improves the thermal conductivity of Jeffrey Nano-fluid over the Oldroyd-B and Maxwell Nano-fluids. The model active for the Nano-liquid flow of Jeffrey, Maxwell and Oldroyd-B fluid encloses the Brownian motion parameter effect. Study mainly focused to understand the physical appearance of the embedded parameters based on the characteristic length of the liquid flow. The obtained results are drafted graphically and discussed.