Embryonic brains, skin, heart or lungs were dissected from pregnant females at E15.5 and E17.5 and postnatal brains from P0 and P7 pups. P22 mice were euthanized with isoflurane overdose and the brains were perfused with 4% paraformaldehyde (PFA). All other brains and organs were drop fixed in 4% PFA overnight. Immunohistochemistry was carried out essentially as described previously on 50 μm-thick Vibratome sections (Ma et al. 2012 (link), 2013 (link)). Primary antibodies or reagents used include biotinylated isolectin B4 (Vector Lab), rat anti-mouse CD31 (BD Pharmingen), rabbit anti-GFP (Life Technologies), rabbit anti-Brain lipid binding protein (Millipore), rabbit anti-Desmin (Millipore), mouse anti-NeuN (Millipore) and rat anti-mouse endomucin (Affymetrix eBioscience). FITC or Cy3 conjugated secondary antibodies were purchased from Jackson ImmunoResearch Laboratories (West Grove, PA). Images were taken under a Nikon eclipse Ti microscope and processed using Adobe Photoshop CS6.