The present invention provides methods of reprogramming cells, for example, directly reprogramming a somatic cell of a first cell type into a somatic cell of a second cell type, are described herein. In particular, the present invention generally relates to methods for reprogramming a cell of an endoderm origin to a cell having pancreatic β-cell characteristics. The present invention also relates to an isolated population comprising reprogrammed cells, compositions and their use in the treatment of diabetes mellitus. In particular, the present invention relates to reprogramming a cell of an endoderm origin to a cell having pancreatic β-cell characteristics by increasing the protein expression of at least one transcription factor selected from Pdx1, Ngn3 or MafA in the cell of endoderm origin to reprogram the cell of an endoderm cell to a cell which exhibits at least one or at least two characteristics of an endogenous pancreatic β-cell.