To standardize human embryonic stem cells is an exercise in standardizing different kinds of unknowns. Such standards, currently being developed in the field, can change the understanding of what a stem cell is. In the influential International Stem Cell Initiative (ISCI), scientists in a fiercely competitive field are prepared to exchange research material and data that would normally be highly confidential. ISCI participants understand the particular unknown that they are seeking to standardize as a 'known unknown' and hope that their collaborative work will serve to move the field forward and thus enable both competition and comparable data. Such known unknowns are seen to be of vital importance, yet of a different epistemic currency than the types of unknowns that could lead to scientific fame and fortune. Furthermore, while the notion of 'pluripotency' is of pivotal importance as a discursive resource when demarcating the abilities of embryonic stem cells from those of adult stem cells, it can also present a practical problem. A more flexible definition allowing for different stem cell 'niches' could render the cell lines less pluri but more potent. The reconfiguration of pluripotency may serve to transport human embryonic stem cells into a clinical and 'doable' future.