Antimicrobial peptides (AMP) are evolutionary ancient molecules produced by nearly all living organisms, both prokaryotic and eukaryotic cells. More than 2000 AMPs have now been identified. These peptides are produced by most human cell types, such as those in the skin and mucous membranes and blood. Each tissue has a different spectrum of AMPs. Antimicrobial capacity depends on the structural characteristics such as charge and amphiphilicity that allow the insertion and/or penetration of AMP into the membranes of microorganisms or other cells. AMPs may have importance in the pathogenesis of neurodegenerative diseases and type 2 diabetes. The most investigated AMPs are defensins and cathelicidin LL-37.