Quantum science and engineering provides new insight into how the physical world can be measured.  As the quantum behavior of a system is preserved for longer periods of time, it becomes more sensitive to environmental perturbations.  While this poses a challenge for the long-term goal of quantum computing, it provides a new opportunity for sensing, an area where near-term impact is expected.  Exquisite control over individual quantum sensors allows for high precision and high spatial resolution, and fundamental limits to sensitivity can be improved by using quantum information concepts such as entanglement. This toolbox creates new opportunities: ultrahigh precision timekeeping, navigation, precision measurement to test fundamental physical theories, and sensors for diverse applications from probing biological systems down to the single molecule level, sensing in extreme environments, and biomedical applications.