Treussart uses fluorescent nanodiamonds (NV centres) as photostable bio-probes: intracellular single-particle tracking, nanoscale thermometry/magnetometry, and multimodal biosensing in cells and organisms, alongside super-resolution imaging - a direct NV-ensemble-to-biology bridge. In the broader landscape of NV-centre ensemble quantum sensing (DEER, nano-NMR, T1 relaxometry) operating near pT/sqrt(Hz) sensitivity, this work is applied here to living cells via nanodiamond probes.