Gold nanoparticles have been at the centre of attention in nano-science and technology due to their extraordinary optical and physical properties. Recent advances in sensing and cell biology area include strong nonlinear absorption, luminescence enhancement and plasmon-coupled ruler in the 1- 20 nm regimes. While many applications are being demonstrated, fundamental understanding of these advances is still lacking. Where and how does the metal luminescence come from? How does the shape play a role in the luminescence? What are the material limitations? Is the stability of particle shape critical in success of these applications? How does the reshaping of these particles occur? In this talk, I will present recent spectroscopic studies of single gold nanoparticles (luminescence, scattering and correlation spectroscopy) at Optical Nanomaterial Spectroscopy group in addressing these important questions for the future success of its applications. Recorded on 8 May 2015.