Stem cells in the bone marrow can be forced into blood vessels in a process called mobilization. Mobilization of stem cells from the bone marrow into the blood vessels represents the basis for modern bone marrow transplantation procedures.

To test the effect of light on the mobilization of stem cells, mice were subjected to a simulated "jet lag" by advancing the light-dark cycle by 12 hours. This was done by subjecting mice to a 24 -hour light period before the results shown in the graph were recorded. The results were compared to the stem cells in control mice under normal conditions of 12 hours of light ( □ ) and 12 hours of darkness ( dark box) and 12 hours of darkness ( dark box ).