Transwell-based assays are widely used to assess cancer cell migration and invasion. Migration is the movement of cells from one location to another and is central to the metastatic cascade. Cell migration may be random or directed by gradients in soluble factors, electric field, or matrix stiffness. Invasion refers to the migration of cells in a 3D ECM. The three commonly used variations of transwell-based assays are (1) migration assays, (2) invasion assays, and (3) transendothelial migration assays (Table 2). Migration, the simplest variation, involves seeding cancer cells directly on a porous membrane, while invasion assays involve seeding cells on a layer of ECM material on top of the porous membrane .