The mechanisms governing self-organization  have long been a subject of interest for a large community of physicists, chemists and engineers, with the implicit desire to harness self-assembly for fabrication processes. These efforts have had limited success since self-assembly relies on thermodynamics and is prone to large deviation. Remarkably, biological systems self-organize continuously with little errors on many length scales, in highly noisy conditions. Biological self-organization is active both in the sense of energy consuming polymerization and in the use of molecular motors to drive assembly.  Recent experiments aimed at elucidating the fundamentals of active self-organization have used model systems, such as the in-vitro actin/myosin cytoskeleton model, to isolate the process of cytoskeletal self-organization. Here we demonstrate that unlike kinesin and dynein that walk on top of microtutbules, myosin motors are an essential part of the actin network itself. Acting as internal active cross-links and applying local stresses as high as 50pN, myosin II motor clusters are not only embedded in the network, but also take a leading role in dictating its structure and dynamics. The stresses building-up in these networks lead to complex dynamics and can drive their contraction and rupture, depending on motor concentration and cluster size.