Muscles are the engine of our body, and actomyosin is the engine of a cell. Both muscle and the actomyosin use the same proteins, namely, actin, and myosin, which are the pair of cytoskeleton and motor proteins generating a force to realize deformation. The properties of force generation by actomyosin at a single-molecule level have been studied for many years. Moreover, the active properties of higher-order structures integrated by actomyosin are attracting the attention of researchers. Here, we review the recent progress in the study of reconstituted actomyosin systems in vitro toward real-space models of nonequilibrium systems, collective motion, biological phenomena, and active materials.