High hopes have been placed on the introduction of cell-based therapies in medicine. Stem cells are to serve the treatment of degenerative diseases in future, cells of the immune system are to be stimulated and new drugs are to be tested more reliably and without animal experiments, using tissue samples. For all these applications, it is necessary to be able to control the behaviour and development of cells. Adherent cells are important in such therapies. They can grow outside an organism on a surface and can also divide and they will respond to the texture of the surface that they are growing on. We are taking advantage of this by tailoring ultra-thin layers made out of a wide range of polyelectrolytes to suit the purpose of controlling the development of the cells. Additionally, we are modifying the polyelectrolyte layers so that their properties can be switched on and off by external stimuli, such as laser light, making it much easier to use them and extending the range of applications. We now want to examine further the cellular biology, biochemical and physical aspects of this concept and attempt to enhance the potential for biomedical applications.