Newly born taste cells enter taste buds in both circumvallate and fungiform papillae within 12-18 hours of birth. A,E. BrdU-IR cells are present in the basal epithelium and perigemmaly, around taste buds, at 6 hours post-injection in circumvallate papillae (A, transverse section) and fungiform papillae (E); tb = taste bud. B,F. At 12 hours post-injection, BrdU-IR cells are evident around taste buds, and some BrdU-IR cells are found inside taste buds in the circumvallate papilla (B circumvallate; F fungiform). C,G. In both circumvallate and fungiform papillae, BrdU-IR cells are present inside taste buds at 18 hours post-injection (C circumvallate; G fungiform). D,H. BrdU-IR cells reside in the basal compartment and along the inner limits of taste buds by 24 hours (D circumvallate; H fungiform). I,J,K,L. BrdU-IR cells are detected in more central regions of taste buds at 48 hours (I circumvallate; J fungiform) and 72 hours (K circumvallate; L fungiform), but are also still detected in the perigemmal zone (white arrows). Scale bars: 20 μm.