3D halide perovskites are direct band gap semiconductors, with low effective masses, sizeable optical oscillator strenghts. In relation with an original crystallographic structure for a semiconductor, electronic band edges at the R point define 3D halide perovskites as a novel semiconductor class characterized by Sz=1/2 for the top of the valence band and Jz=1/2 for a split-off band at the bottom of the conduction band due to a giant spin-orbit coupling [1,2]. Excitonic properties have been at the center of discussions since the beginning of the hype on photovoltaic in 2012. Following a prediction in 2014 [2], the direct measurement of the exciton binding energy in 2015 [3], led to values strongly reduced with respect to accepted values so far reported. Perovskite photovoltaics is since considered closer to the field of classical semiconductor solar cells than initially expected. The understanding of the excitonic properties, especially the exciton fine structure and the nature of exciton complexes, was further questioned with the advent of perovskite nanostructures leading to prospects for quantum light emission. A debate between an initial proposition of a fine structure related to a singlet dark ground state [4,5] and an inverted dark-bright ordering [6] , was closed recently in favour of the initial proposition [7,8,9]. Several open questions are remaining, especially about the nature of the coupling between the charge carriers and the lattice dynamics, which is unusual with respect to classical semiconductors [10]. Direct experimental investigations on the low energy lattice dynamics including neutron scattering are in progress [11]. State of the art abinitio simulations of the lattice dynamics and electron-phonon coupling will be shown [12]. The regime of low-temperature Fröhlich polaronic coupling in bulk 3D perovskites and quantum dots is also explored.