Lung bud progenitor cells in the tips of the lung buds constitute a pool of highly proliferative multipotent progenitor cells during the pseudoglandular stage. Progeny left behind in the stalks by the outgrowth of the epithelium continue to divide and give rise to all of the different cell types of the future bronchi and bronchioles. Cells in the tips also continue to divide and populate the distal tubules at the canalicular and saccular stages.