The D(p,γ) 3He reaction is responsible for the deuterium destruction during the Big Bang Nucleosynthesis (BBN) and affects the primordial deuterium abundance. This latter is sensitive to fundamental cosmological parameters such as
the baryon density and the effective number of relativistic species. In this paper, we describe the most precise direct measurement of the D(p,γ) 3He reaction in the BBN energy range (Ecm = 30–280 keV) at the LUNA (Laboratory for Underground Nuclear Astrophysics) facility in Gran Sasso National Laboratories. Experimental results, cosmological consequences, and future prospects are reported here