The RHIC beam energy scan program, complemented by similar programmes at other accelerators, allows for the investigation of the phase diagram of QCD matter by varying the beam energy in the region where the change from crossover to first order phase transition is suggested to occur. The nature of the quark-hadron transition can be studied through analyzing the space-time structure of the hadron emission source. Many measurements were performed in the recent years, from particle yields through fluctuations and anisotropies to intermittency and quantumstatistical correlations. These as of now show a controversial picture, and in this talk, we will go through the plethora of results, with special focus on Bose-Einstein correlations.