We report the evolution of the lattice, electronic and magnetic structure of nickelates along the series using various optical spectroscopy techniques. The crystal structures from the highest to the lowest symmetry present in the phase diagram, the electronic structure and the different probable magnetic orders below the Neel temperature are described in detail. A general introduction on optical and Raman spectroscopies as well as descriptions of different optical measurement techniques are also presented. We show the optical properties of LaNiO3 films tuned from compressive to tensile strain, which shows an evolution of free carrier spectral weight and mass enhancement as a function of strain. We report the Raman spectroscopic evidence for multiferroicity in rare earth nickelate single crystals (R=Y, Er, Ho, Dy, Sm and Nd), which shows the appearance of new optical modes below the Neel temperature. We show also the impact of pressure on SmNiO3 and NdNiO3 single crystals.