Using collective spins or nanomagnets offers the possibility of constructing high speed nonvolatile electronics, resulting in the energy dissipation at the device level possibly approaching the fundamental equilibrium Maxwell-Shannon-Landaur limit. This paper will describe the progress in energy-efficient MgO-based magnetic tunnel junction (MTJ) bits for high-speed spin-transfer-torque magnetoresistive random access memory (STT-MRAM). Furthermore, the possibility of a Magnetoelectric RAM (MeRAM) as a promising candidate for ultralow power is discussed. Demonstrated principles and experiments of voltage-induced switching of the magnetization and reorientation of the magnetic easy axis by electric field offer much reduced switching energy at high speed. The latter may enable a new paradigm of high speed nonvolatile electronics.