Mechanical forces play an important role in the organization, growth, maturation, and function of living tissues. At the cellular level, the transmission of forces from outside the cell through cell-matrix and cell-cell contacts are believed to control spreading, motility, maturation as well as intracellular signaling cascades that may change many characteristics in cells. We looked at cell populations of mouse embryonic fibroblasts that are deficient of focal adhesion kinase (FAK) and examined their mechanical profile. We observed that the lack of FAK induces a mesenchymal-epithelial switch including the regulation of adherens junctions via E-cadherin, leading to increased cell-cell-cohesion. Our results show that the absence of FAK influences the macroscopic cell colony spreading in two (2D) and three (3D) dimensions as well as the velocity fields of the tissue, the single cell persistence and correlation length, changing from an independent to a collective mode of migration. Additionally, the single cell size in the sheet decreases significantly. (C) 2013 Elsevier Inc. All rights reserved.