Quantum science and technology rests on our understanding and control of matter and information at the smallest scales. Devices based on individual atoms or complexes of a few atoms represent the ultimate limit in a process of miniaturization that has been happening since the beginning of the semiconductor era. Indeed, certain arrangements of atomic impurities in semiconductors – known as quantum point defects (QPDs) – exhibit quantum-mechanical features like isolated atoms or molecules, but in room-temperature devices amenable to integration and miniaturization. In this talk I will discuss recent advances in our ability to control quantum states in semiconductor devices, including multi-qubit quantum memory nodes and nanoscale quantum sensors based on well-known nitrogen-vacancy-center QPDs in diamond. I will also highlight efforts to identify and engineer QPDs in new materials – especially two-dimensional hexagonal boron nitride – that will expand the potential for exploring fundamental physical phenomena and realizing novel quantum technologies.