During gastrulation, intricate cellular rearrangements establish the three germ layers of the embryo. As part of this process, the progenitor cells of the different layers acquire specific adhesion properties. These properties are thought to be modulated by Wnt signaling. On p. 4199, Pierre-Henri Puech, Carl-Philipp Heisenberg and co-workers provide the first direct evidence for this hypothesis by using atomic force microscopy to measure the strength of the adhesion between individual primary gastrulating zebrafish cells and fibronectin-coated substrates. They show that mesendodermal progenitor cells from zebrafish silberblick mutant embryos, which carry a loss-of-function mutation in the wnt11 gene, require less force to remove them from a fibronectin-coated substrate than do wild-type cells. Other results indicate that this difference results from the reduced adhesion of the wnt11 mutant cells through integrins to the fibronectin substrate. Thus, the authors conclude, Wnt11 signaling modulates cell adhesion during gastrulation, possibly by regulating integrin expression/localization in the mesendodermal progenitors.