Formalin-fixed FFs embedded in paraffin were sectioned and stained with HES. (A) Overview of a typical FF with a growing feather after microdissection. bbr, barb ridges; cb, collar bulge; dermis; fs, feather sheath; follicular wall; fp, feather pulp. An enlargement of the barb ridges is shown. (B) Structure of FF after 1 (D1), 3 (D3), 6 (D6), and 7 (D7) days of cultivation in vitro. A low magnification showing the whole FF with its feather (left panels). An enlargement of the barb ridges (right panels).</p