Labeling of human peripheral blood CD34⁺. Human primary CD34⁺ cells were seeded at a concentration of 500 000 cells in 200 μL stem cell media; 1 μL/mL fluorescent particle suspension was added to the well, and the cells were incubated at 37°C for 18 hours. The cells were collected, washed, and resuspended on a chamber slide for microscopy. The left panel shows light microscopy images of the cells, showing a uniform population of primitive hematopoietic progenitors with no evidence of toxicity and some cells undergoing active cell division; original magnification, × 100. The right panel is a fluorescent micrograph of the same field, showing that more than 90% of the cells fluoresce green, with relatively homogeneous intensity; original magnification, × 100. The inset is a higher-power view (× 1200) of a fluorescent cell in the midst of mitosis, with segregation of the label occurring to both daughter cells.