Murine fetal-lung explant cultures produce HSPCs. (A) Images of a single position between days 3 to 6 of a murine fetal-lung explant culture. (B) Cytospin of fetal lung–derived suspension cells. Images are annotated for cell type: MK, megakaryocyte; N, neutrophil; M, monocyte/macrophage; P, progenitor. (C) Images of representative colonies from a colony-forming unit assay. (D) Colony counts from colony-forming unit assays performed with day 4, 5, 6, and 8 bulk unsorted suspension cells. Each n represents a set of colony assays with at least 3 technical replicates from a distinct biological replicate. (E-G) Flow cytometric assessment of LSK and SLAM marker–defined HSPC populations. Each n represents a biological replicate with a minimum of 3 technical replicates per experiment. Suspension represents cells that were floating in media, and adherent represents cells that were collected after treatment with Accutase. Error bars represent standard error. ∗P < .05, ∗∗P < .01.