Archaea, one of the three domains of life, are a highly diverse group of prokaryotes that include a number of extremophiles.[1] One of these extremophiles has given rise to a highly complex new appendage known as the hamus (pl.: hami). In contrast to the well-studied prokaryotic appendages pili and fimbriae, much is yet to be discovered about archaeal appendages such as hami.[2] Appendages serve multiple functions for cells and are often involved in attachment, horizontal conjugation, and movement. The unique appendage was discovered at the same time as the unique community of archaea that produces them. Research into the structure of hami suggests their main function aids in attachment and biofilm formation. This is accomplished due to their evenly placed prickles, helical structure, and barbed end.[3] These appendages are heat and acid resistant, aiding in the cell's ability to live in extreme environments.[4]