Microfluidic devices offer a realistic environment for cell cultures as it is related to scales found in biological systems. The aim is to create more in vivo like systems, in comparison to 2D plate cultures. Creating 3D cell culture constructs increase the cell's functionality. By controlling the microenvironment (e.g., cell matrix, flow rate, temperature) cell functionality can be increased even more. As microfluidic devices allow for precise control of the microenvironment, they are a paramount tool to study stem cells and their differentiation caused by external factors. We will give an overview of the use of microfluidic devices for some biological problems, and especially as a cell culture platforms. We focus on 3D cell cultures and stem cells and their microenvironment.