In the western world, until recently people did not think about sleeping on a well-designed system. Instead they slept on worn-out mattresses and sagging bed bases. Later on, firm beds were promoted for the prevention of low back pain; as a result, many people started to put wooden boards in between the mattress and the base. This solution, however, does not help improve the supporting qualities of a bed, and might even cause ventilation problems. Today, the definition of a correct sleeping system (i.e. mattress base head cushion) is much more differentiated, and involves physical, physiological, and psychological factors. This entry discusses these factors and illustrates how different parts of a sleeping system can be designed and combined, depending on personal need, and bearing in mind that most properties are not designed for life: even a fatigue-resistant mattress loses 10 to 15% of its elasticity within 10 years.