The nitrogen-vacancy (NV) defect centre in diamond represents an ideal single spin quantum system for use as a new probe in biology. It possesses a broad absorption band from 512-560 nm, sustained fluorescence from 630-750 nm, is chemically inert and bio-compatible. These defect centres have been used as highly stable fluorescence beacons to track the position and diffusion of diamond nano-crystals in vitro [1,2] and in vivo . Recent experimental demonstrations  of nanomagnetometry using these single spin systems create opportunities for new applications in biology . In our work, we explored the viability of diamond-based nanobiomagnetometry by performing the full suite of quantum control and measurement protocols on NV-nanodiamonds in a living HeLa cell , and demonstrated nanoscale spin detection in the biological context .