This article is the companion of an invited overview talk given at the H-Mode Workshop 2019. Quantitative predictions of the L to H power threshold are needed to prepare the 'pre-nuclear' ITER operation in H or He, as well as to design a future fusion reactor where the confinement regime interplay with divertor configuration, radiation level, etc has to be understood. With this urgency in mind, this article aims at sharing references and views on advances on the L to H transition physics understanding. It reviews L mode edge turbulence drive understanding as well as the mechanisms at play behind the shear. It shows that our understanding is mature enough to finally model a pedestal formation above a given power threshold using flux driven physics-based models. It shares views on future directions to take, to challenge and hopefully confirm these encouraging results.