Abstract: An assembly for in vitro culture of cells of the present invention includes a culture vessel with at least one well. The well has an open top, a bottom and a wall with an inside surface. The assembly also includes at least one insert sized for placement within the well. The insert has an outside surface, an open end and a closed end. There is a microporous membrane at the closed end of the insert that closes the end and thereby forms a receptacle within the inset. The assembly further includes provisions for adjustably positioning the insert within the well between a first position where the closed end of the insert is a first distance from said bottom of the well and a second position where the closed end of the insert is a second distance from the well bottom.