My research interest lies in understanding how particle size and morphology can affect physical properties of nanomaterials, in particular their optical properties. I currently develop solvothermal synthesis methods to get accurate control of size and crystal quality of oxide nanomaterials (garnets, iodates, perovskites). During this presentation, I will mainly focus on the elaboration of garnet-type nanocrystals doped with Ce³⁺ or Nd³⁺ for solid-state lighting and bio-imaging applications. We succeeded in obtaining nanometer-sized single-crystals in the range 30 to 200 nm. Their high crystalline quality allowed us to observe intense rare-earth luminescence, which is promising for their use as phosphors or as bio-probes for in vivo nanothermometry applications.