These days, all introductory biology students know that sliding filaments of myosin and actin cause muscle contraction. Moreover, cell biology students learn that there are more ubiquitous, less specialized forms of cell motility than what is evident in contracting muscle cells. Increasingly, it seems that actin is involved in a wider variety of motility phenomena than can be accounted for simply by the sliding movement of stable filaments. These phenomena rely not only on different types of myosins but on a different property of actin, namely, its highly regulated assembly and disassembly. The sliding and assembly/disassembly paradigms are explored in the first set of videos described in this essay. The second set focuses on the subtle but crucial importance of cell attachment in all forms of locomotion and specifically on the role of integral membrane proteins in mediating the attachment of assembling and sliding filaments in the cytoplasm with the extracellular substratum. (Contains 3 figures.)