Blood contains different types of specialized cells. Red cells are responsible for oxygen transport, white cells ensure body's defense against infections, and platelets initiate clotting to limit the loss of blood after an injury. These cells are constantly renewed, and are manufactured in the centre of the bones in a sponge-like tissue called bone marrow. Hematopoietic stem cells are a small subset of cells found in bone marrow that have the astounding ability to self-renew and divide, and to differentiate into a variety of mature blood cells. They are often used to treat blood-related diseases or given after cancer treatment. Although stem cells have great potential for regenerative medicine, they are extremely rare and they are difficult to expand in the lab, because they very readily differentiate into other cell types. The multiple factors that influence their self-renewal are poorly understood. Véronique Lecault is exploiting the potential of microfluidic technology, an engineering advance that allows thousands of different experiments to be performed in tandem upon a device the size of a microscope slide. Across rows and rows of miniature cell culture chambers, individual hematopoietic stem cells can each be exposed to different chemical conditions and tracked over time. This makes determining the specific environments that will allow the cells to be expanded much more efficient. This technology could lead to the ability to produce more hematopoietic stem cells for use in disease therapies. It could also help researchers gain a better understanding of stem cell biology, perhaps leading to the discovery of new ways to identify and purify these rare cells.