This book examines the channels and pores that belong to an eclectic and ubiquitous class of unconventionaland arguably, sometimes strangepore-forming molecules, which fulfill fundamental roles in various organisms. These non-canonical channels may take on various and sometimes complex architectures, such as large beta-barrels or lipid-containing pores and may originate from bacteria, viruses or intracellular organelles. For some of them, the physiologically relevant substrate may indeed be ions; for others, it consists of folded polypeptides. Some are released by cells in a soluble form that can pass through biological membranes to exert its permeabilizing effect. Many of these unconventional pores have been investigated by electrophysiology, which, by virtue of its focus on a few or even a single unit, has provided invaluable insights into the mechanisms and structure-function relationships of these remarkable membrane entities. The respective chapters of this book highlight a representative set of these interesting investigations.