The astonishing display of stars on a clear night sky has, since before the emergence of civilizationas we know it, sparked curiosity and guided the principles of our early human ancestors. Theshining cartels of light belong to the Milky Way galaxy, one among trillion starry islands in thevisible Universe which constitute the gravitational nodes of the cosmic assembly. During 13.8billion years of cosmic evolution, the genesis of matter perturbations gives rise to conglomerates ofstars, the giant elliptical galaxies, a homogeneous population of dynamically hot massive galaxies,devoid of star formation and made up of old stars. These galaxies follow tight scaling relationsthat persist out to high redshift establishing their formation in the early Universe. The adventof near-infrared (NIR) observations and large cosmological surveys have revolutionized modernastronomy by allowing studies of these galaxies in the epoch of their formation, more than 10billion years ago. In this thesis, we investigate the connection between a sample of compactred and dead galaxies, the so-called quiescent galaxies, at redshiftz >2and their assumeddescendant: the giant elliptical galaxies. We employ the study of scaling relations as a tool tounderstand the formation and evolution of massive galaxies over cosmic history.Combining 10 years of international effort, we present the largest (homogeneously) selectedsample of massive quiescent galaxies atz >2from the COSMOS survey with NIR X-Shooterspectroscopy andHSTNIR imaging. The spectra contain information of the galaxies’ distances,stellar masses, ages, and velocity dispersions that, combined with their morphology and sizesfrom imaging, allow for a detailed examination of their stellar and dynamical properties. Thewealth of observations allow for the documentation of their compact structures, high-velocitydispersions and quiescent non-star-forming nature. We show that minor mergers can account forthe size evolution for massive quiescent galaxies over the span of 10 billion years. Furthermore,we nd that the evolution of the Fundamental Plane scaling relations, into present-day massiveelliptical galaxies, can be characterized by passive evolution of the stellar population togetherwith signicant size growth by minor mergers with quenched stellar populations.