The Critical 2d Stochastic Heat Flow arises as a non-trivial solution to the Stochastic Heat Equation (SHE) at the critical dimension 2 and at a phase transition point. It is a log-correlated field which is neither Gaussian nor a Gaussian Multiplicative Chaos. We will review the phase transition of the 2d SHE, describe the main points of the construction of the Critical 2d SHF and outline some of its features and related questions. This will be mostly based on joint works with Francesco Caravenna and Rongfeng Sun but contributions from other researchers in this endeavour will also be mentioned.