In this talk we will review the foundational physics arguments for the occurrence of the phenomenon of gravitational lensing as predicted by Einstein’s general theory of relativity (GTR). A short review of the Einstein’s equations formulated by 1915 and the successful observational confirmations of the theory, in particular the August 2017 spectacular direct detection of the spacetime curvature waves, i.e. gravitational waves, from merging of a neutron star binary, as seeing by LIGO and VIRGO gravitational-wave observatories. Some comments on Einstein’s pathway to predict such phenomenon will be offered, and the specific expression to short-hand computing the angular deviation of background stars around the Sun field of view, will be given. In the offing, we shall briefly digest on the overall implications of such an achievement on May 29, 1919 for our understanding of the universe we live in.