Heads and femora were dissected from 3 week or 3 month old mice, fixed with 4% PFA for 4h, cryoprotected with 30% sucrose for 2 days, embedded in 8% gelatin, and cryosectioned at −25 °C. Slides were used for immunodetection against SOX9 (red). Nuclei were stained with DAPI (blue) (B, D, F, H, J). Adjacent sections of those tissues were used for Hematoxylin & Eosin (H&E) staining (A, C, E, G, I). Arrow heads in A and B indicate growth plate and in G and H, articular cartilage. Arrows in A and G indicate trabecular bones and in C, D, I, and J, nasal septum. DM = dental mesenchyme, DE = dental epithelium, FM = follicle mesenchyme. Scale bars = 50 μm.