Fig 2B. [doi:10.1242/dev.006221] Copyright: This image is from Chen F; Desai TJ; Qian J; Niederreither K; Lu J; Cardoso WV, "Inhibition of Tgfbeta signaling by endogenous retinoic acid is essential for primary lung bud induction" Development 2007;134:2969-2979 and is displayed with the permission of The Company of Biologist Limited who owns the Copyright. [PMID:17634193]