The invasive growth program under physiological and pathological conditions. In both settings, invasive growth results from analogous biological processes - cell-cell dissociation and migration, cell multiplication, and survival - but the endpoints are different. Normal cells exploit invasive growth to colonize new territories and build polarized three-dimensional structures, thus forming the parenchymal architecture of several organs. Cancer cells implement this program aberrantly to infiltrate the adjacent surroundings and form metastases.