The fungal hydrophobins are small proteins that are able to spontaneously self-assemble into amphipathic monolayers at hydrophobic:hydrophilic interfaces. These protein monolayers can reverse the wettability of a surface, making them suitable for increasing the biocompatibility of many hydrophobic materials. The self-assembling properties and amphipathic nature of hydrophobins make them attractive candidates for biotechnological applications. Recently, there have been significant advances in the understanding of the structure and assembly of these remarkable proteins. This opens up the way for engineering these proteins to encompass novel functions and for the use of hydrophobins in modification of nanomaterials. This review highlights the important structural aspects of the hydrophobins and the mechanisms by which they assemble and describes recent exciting developments in the use of hydrophobins for cell attachment, drug delivery, and protein purification. © 2013 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 100: 601–612, 2013.