PHIBSS2, the IRAM Plateau de Bure High-z Blue Sequence Survey, is a multi-year IRAM PdBI / NOEMA legacy program to investigate early galaxy evolution from the perspective of molecular gas reservoirs. The goal of PHIBSS2 is to investigate whether the evolution of cosmic star formation rate around the peak of massive galaxy formation 10 Gyrs ago was mostly driven by available cold gas reservoirs, and the balance between gas inflows and outflows. PHIBSS2 will explore the cold gas content at high stellar masses, in the ‘quenching’ regime, and will study the impact of AGNs and growing bulges. The project will investigate the evolution of the relation between cold gas masses and star formation on galactic, sub-galactic and local scales. PHIBSS2 is phased to optimize and exploit the NOEMA capabilities as they come online and will tackle a unique set of questions at the heart of galaxy evolution.