We present an overview of our results demonstrating a large, charge-driven, magnetoelectric coupling in epitaxial Pb(Zr0.2Ti0.8)O3/La0.8Sr0.2MnO3 (PZT/LSMO) multiferroic heterostructures. Measurements of the magnetization as a function of temperature and applied electric field using magneto-optic Kerr effect magnetometry show a large change in the magnetic critical temperature and magnetic moment of the LSMO layer for the two states of the PZT ferroelectric polarization, which modulates the charge-carrier concentration at the LSMO interface. Near-edge x-ray absorption spectroscopy measurements show directly that the valence state of Mn is modulated by the PZT polarization state, demonstrating that the magnetoelectric coupling in these PZT/LSMO multiferroic heterostructures is purely electronic in origin. From the combined spectroscopic, magnetic, and electric characterization, we conclude that both the interfacial spin state and spin configuration are modulated electrostatically. This ability of controlling spin by means of electric fields opens a new venue for the development of novel spin-based devices.