During the last reporting period we have continued to develop technology that allows non-invasive real time imaging of living stem cells in their natural state and can allow stem cells to be distinguished from their most closely-related differentiated derivatives. The methodology has been developed such that we will soon be able to measure the absolute concentration of specific metabolites within living cells. This in turn will allow the concentrations of such metabolites to be compared between cell types, thus enabling comparative studies of stem cells and closely related daughter cells and stem cells and their in vitro counterparts. In the long run these studies should provide new information about how pluripotent stem cells normally develop and how their development may be impaired by environmental factors. This information in turn could help us understand more about normal human development and how it can all too often go wrong. Studies of adult stem cells in tissues could also allow us to understand what factors affect normal growth of stem cells in tissues and how that process can go awry in the development of cancer.