Peptide molecules exhibiting antimicrobial properties are found in nature as a product from animals, plants, or microbes. Additionally, peptide molecules can be synthesized in chemical laboratories covering in principle an unlimited extension of chemical structures, sequences, and spectra of action. The use of peptides as antimicrobials has been relatively extended in industrial microbiology. Lantibiotics and bacteriocins from lactic bacteria have been used as food preservatives worldwide. In the past few years, the eventual application of such molecules to fight against infectious diseases is growing due, in part to the narrow investment in searching for new antibiotics and the increasing number of infectious diseases caused by multi-drug resistant bacteria. The mechanism of action of antimicrobial peptides involves in general membrane damage but they act also on internal targets, such as protein synthesis, folding and translation, cell division and DNA/RNA synthesis. Thus, such agents can have not only antibacterial but also antiviral and antifungal activities. The study of damage caused by antimicrobials into the membranes is a powerful approach to explore chemical modifications and strategies of delivery that can enhance the antimicrobial activity of such compounds. In this chapter, different kinds of antimicrobial peptides, their chemical structure, antimicrobial action and mechanisms are reviewed. Single channel conductance measurements are used to explore the properties and nature of peptide/membranes interaction.