Alizarin red S staining of osteogenically primed, sorted stromal vascular fraction cells. Primed, sorted SVF cells were differentiated down the osteogenic lineage for 3 weeks and stained for calcified matrix deposition (control medium conditions shown in insets). ALPL+ cells visually produced the most matrix, with very dense, consistent staining across the entire sample. ALPL– cells produced the least matrix, with the stain appearing as a slight wash of orange–red across the culture surface. Unsorted cells produced some matrix, but deposition was scattered, with some areas appearing very red and others unstained. Scale bar: 100 μm. ALPL, alkaline phosphatase liver/bone/kidney.