Transplantation of the presumptive thyroid explants into the embryo flank is sufficient to cause expression of sftpb in the explant. When explants of the presumptive thyroid region are cultured alone, they do not express sftpb (A) but do express pax2 (B - black arrows). Note that the small blue flecks are seen on the surface of many embryos due to the stickiness of the cement gland that is also usually in part of the explant. When those same explants are placed on to the flank region immediately after they are removed from donor embryos, sftpb expression can be seen in the explant (blue arrows) as well as the endogenous lung (green arrows). When explants are transplanted, expression of pax2 (red arrows) can be seen in the explants. Embryos in C and D are normal views and embryos in E and F have been cleared to better visualize staining although cavity staining is also seen when embryos are cleared.