The boundary between quantum and classical physics is continually evolving, with nano- and micron scale mechanical oscillators very recently entering the quantum regime. In this talk, I will demonstrate two types of coherent control of a mechanical oscillator with a precision at the quantum level. In the first, the state of an itinerant microwave field is coherently transferred into and retrieved on-demand from a mechanical oscillator. In the second, the state of the mechanical oscillator is entangled with an itinerant microwave field. Mastery of the quantum state enables us to explore the fundamental quantum limits of measurement and consider applications in quantum information processing. For example, I'll highlight the role of vacuum fluctuations and how specific measurement strategies can circumvent them. I will also discuss the microwave techniques that made near quantum-limited measurements possible and how they benefit a diverse set of experiments, from particle physics to quantum computing.