Researchers used a breast cancer cell line panel and primary tumor explants from breast and cervical cancer patients to examine two different cellular contractility modes: one that generates collective tissue surface tension that keeps cell clusters compact and another, more directional, contractility that enables cells to pull themselves into the extracellular matrix. They found that more aggressive cells pull more strongly on the ECM than on themselves while noninvasive cells pull more strongly on themselves than on the ECM -- and that the different pulling behaviors are attributed to different structures of actin cytoskeleton inside the cells.