The present invention is based on the seminal discovery that cord blood (CB) and adult bone marrow (BM) CD34+ cells can be reprogrammed to early stem cells. The invention provides the reprogramming of CB and adult bone marrow (BM) CD34+ cells from subjects without any pre-treatment. Provided are methods for reprogramming blood cells of a subject. Also provided are methods of disease modeling and methods of generating subject-specific differentiated cells. In addition, the invention provides methods of identifying an agent that alters a function of subject-specific differentiated cells as well as isolated pluripotent or multipotent stem cells reprogrammed from blood cells.