CD34 is a well-known marker for primitive and bone marrow-derived progenitor cells, especially for hematopoietic and endothelial progenitors. Bioarray offers CD34+ progenitor cells in a phenotypically undifferentiated state. The progenitor cells are derived from the peripheral blood of healthy donors that have undergone G-CSF mobilization. Progenitor cells contain two main cellular subpopulations, hematopoietic and endothelial progenitor cells. CD34+ progenitor cells are suitable for a series of studies for directed differentiation into more committed types of blood cells and endothelial lineages. Immediately after isolation, the freshly prepared CD34+ progenitor cells are cryopreserved.