If harvesting cells from your placenta makes you queasy, and it's too late to access some umbilical cord blood, there's yet another medical waste product that may provide a new, uncontroversial source of stem cells: menstrual blood. Dr. Amit Patel from the University of Pittsburgh found that the uterine lining, which is shed during menstruation, contains millions of stem cells. These cells are multipotent (can give rise to several different cell types) and have the capacity for self-renewal—two essential properties of stem cells. The study showed that menstrual stem cells (MenSCs) could differentiate into cells that give rise to fat, cartilage, bone, skin, muscle, heart, and brain cells (though it's important to note that the MenSC's did not actually differentiate into these cells—only into their predecessors). The cells actually showed greater potential capacity than bone marrow mesenchymal stem cells, as they had some of the same properties as human embryonic stem cells. So, how to save your valuable period blood? Dr. Patel partnered up with Cryo-Cell International, the company that brought you cord blood storage for your infant, has now launched the first-ever proprietary menstrual stem cell service. C'elle ("See-El"), as the service is called, costs $500 and allows you to collect and FedEx your menstrual stem cells for preservation. According to the Web site, "you’ll receive an attractive, discreet C’elle collection kit by FedEx delivery. Inside, you’ll find everything needed for you to collect and send your C’elle menstrual stem cells for processing and preservation, including a menstrual cup, collection tubes, prepaid FedEx airbill for return shipment to Cryo-Cell, and comprehensive instructions for use." The cells have yet to be tested in humans, and there are already concerns that banking your baby's cord blood might not be as helpful as you'd like to think. While the medical community supports public banking of cord blood, it (along with many governments) has reservations about private banking. The European Union Group on Ethics stated that (pdf) "the legitimacy of commercial cord blood banks for autologous use"—reimplantation into the same individual they came from—"should be questioned as they sell a service, which has presently, no real use regarding therapeutic options. Thus they promise more than they can deliver. The activities of such banks raise serious ethical criticisms." At present, MenSC therapies are even more limited—and the logic of paying money to store something many will see for several days every month is questionable—but both it and cord blood have great potential. MenSCs are now being tested in pre-clinical (non-human) studies related to potential cardiovascular, diabetes and neurodegenerative human therapies.