Electrical impedance measurements for mouse embryonic stem cells (mESCs) were performed to study the embryonic stem cell differentiation process. The electrical frequency response (e.g. impedance magnitude and phase) of individual stem cells during the course of differentiation has been studied. Electrical parameters (e.g. permittivity and conductivity of cell membrane, cytoplasm, nuclear membrane, nucleoplasm, etc.) of stem cells at different differentiation states have been extracted and quantitatively analysed.