Sleeping well is a crucial factor contributing to our physical and mental restoration. Slow-Wave sleep (SWS) in particular has a positive impact for instance on memory and the functioning of the immune system. During periods of SWS, growth hormones are secreted, cell repair is promoted and the defense system is stimulated. If you feel sick or have had a hard working day, you often simply want to get some good, deep sleep, a wish that you may not be able to influence through your own will.