Fibronectin (FN) is an important extracellular matrix (ECM) component that supports cell migration and deformation, as well as integrates cells into functional ensembles of tissues.Here,we demonstrate that FN fibrils are deposited as pillars between the somites and endoderm.Time-lapse imaging analysis of fluorescent-labeled embryos revealed that the basal surface of somitic epithelial cells have long, protruding filopodia-like pseudopods that penetrate the basement membrane to reach the FN pillars.