In this work, we introduce the model of micropolar fluids. We derive equations of motion from conservation laws under a number of suplementary assumptions such as isotropy, Fourier’s law and incompressibility. It turns out that the micropolar fluid model represents a significant generalization of the classical, Navier-Stokes model. Physically, a micropolar model is suitable for fluids whose molecules can rotate independently of the fluid stream flow and its local vorticity. The derived model is considered for two different flows and various boundary conditions. For Poiseuille and Couette flow the influence of the microstructure on the exact solution for the velocity and microrotation is shown. One can conclude from the results that the characteristic geometrical dimension such as the distance beween the parallel planes has significant influence on the effective flow. Once these dimensions are small enough micropolar model is applicable, with the dominant microviscosities and microrotations the change is observed even in the velocity of the flow. For wider channels and such, the flow is quiet well described by the classical, Navier-Stokes equations.