Model depicting the role of basement membrane dynamics in hair follicle morphogenesis. This model illustrates the spatially distinct molecular and tissue-level dynamics of the BM, highlighting its pivotal role in regulating cell and tissue dynamics during hair follicle morphogenesis. The green lines indicate BMs. Magenta cells and BM zones are highlighted tracer epithelial basal cells and BM zones, respectively. The blue cells are epithelial progenitors that divide horizontally relative to the BM, and the red cells are epithelial progenitors that divide perpendicularly to the BM. In normal hair follicle development, the following key features are observed: (1) the rates of COL4A2 turnover and BM expansion exhibit spatial gradients, and these processes are coupled; (2) epithelial progenitors undergo both horizontal and perpendicular divisions; (3) basal epithelial cells move in unison with the directionally expanding underlying BM; and (4) the epithelial tube results in directional elongation. In MMP inhibitor-treated hair follicles: (1) COL4A2 turnover and BM expansion are restrained; (2) progenitors alter the angle of daughter cell allocation from horizontal to perpendicular; and (3) directional epithelial elongation is halted, resulting in a wider organ shape.