A fourth method used to form induced pluripotent stem cells is direct reprogramming. This is the most recent process developed. This process involves reprogramming a somatic cell by adding selective transcription factors that will make it pluripotent. The factors used are Oct4, Sox2, c-myc, Klf4, and nanog. These transcription factors are either introduced into the somatic cell through a viral vector or nonviral vector. The DNA must be reprogrammed to a state that is similar to its state during embryonic development. The transcription factors allow for the somatic cell to become pluripotent and not use any embryonic stem cells.