Due to their self-assembly properties, S-layer proteins are very interesting for being used as biomolecular building blocks for \E2??bottom up\E2?? approaches in nanotechnology. For example, there are applications that use S-layers as biotemplates for the production of metal nanocluster arrays or the functionalization of sensor surfaces. First, the talk will give an overview about the basics of S-layer proteins including the localization, common properties, the preparation of S-layer suspension, opportunities of microscopic investigations, and the preparation of monomer solutions for recrystallization. Then, some S-layer applications will be presented. The use as biotemplate for nanocluster arrays (metalisation) will be explained in detail. Some technics to integratie S-layers into microelectronical devises and two novel methods for coating structural sensor surfaces are introduced as well.