This chapter presents the motivation and context for exploring macroscopic quantum phenomena using optically levitated nanoparticles. It first reviews the evolution of optomechanical systems and emphasizes the importance of levitated platforms in applications such as sensing, thermodynamics, and material science. It then introduces recent advances in cooling techniques for levitated nanoparticles, highlighting the current progress toward realizing quantum phenomena with macroscopic objects. Finally, this chapter outlines the main achievements of this thesis, including the ground-state cooling of translational motion of a neutral nanoparticle, the control of all six mechanical degrees of freedom, and direct velocity measurements via Time-of-Flight experiments.