Quantum superposition and entanglement offer deep resources which are ripe for harnessing in practical devices. Superposition incorporates a phase with information content surpassing any classical mixture. Entanglement offers correlations stronger than any which would be possible classically. Together these give quantum computing its spectacular potential, but earlier applications may be found in metrology and sensing. Fundamental progress is being made in the development of quantum devices incorporating electron and nuclear spins which can be controlled with high precision. Fullerene molecules offer remarkable electron spin properties. They can be assembled in single walled carbon nanotubes, and the resulting atomic structures can be imaged using low voltage aberration corrected transmission electron microscopy. N@C60 contains a single nitrogen atom in a cage of sixty carbon atoms, whose spin superposition states are coherent for hundreds of microseconds,and other endohedral fullerenes can be almost as good. Information can be transferred from electron to nuclear spins and back again to give even longer memory times,and can be stored and retrieved holographically in collective spin states. Small tip-angle excitations can be used to demonstrate many of the fundamental principles. Correlated spins can be used for magnetic field sensors that surpass the standard quantum limit. Devices can be made in which the active materials can be imaged with atomic resolution, and whose transport properties can detect a single electron spin. These results open the way for new technologies using the remarkable resources of quantum superposition and entanglement. This kind of quantum nanotechnology also enables fundamental concepts such as reality to be tested experimentally, stimulating new philosophical insights. Somewhat remarkably, these basic studies serve in turn to push the limits of technology, by extending the range of "quantumness" which can be embodied in practical systems.