The nitrogen-vacancy (NV) centre in diamond is an optically addressable single spin-1 electronic system with relatively long coherence persisting at room temperature, making it ideal for a range of nanoscale quantum sensing applications. The NV system is sensitive to local magnetic and electric fields, as well as material properties such as strain and temperature. An exciting direction is the development of the NV centre as a quantum probe for nanoscopic magnetic resonance applications. In this talk, we will briefly review the NV centre and some of the seminal sensing and imaging demonstrations, and focus on new results based on controlled cross-relaxation between the NV quantum probe and target electron and nuclear spin systems. Experimental demonstrations of both electron and nuclear spin resonance using these techniques will be described, including applications in chemical detection, bio-magnetic characterisation, and hyperpolarisation of nuclear spins external to the diamond substrate. Finally, we will look at ideas for using such controllable quantum spin probes in bio-molecular structure determination.