The correlation functions (three and higher point) in N=4 SYM can be computed using integrability techniques. One formalism is called hexagonalization and its main object is an integrable form-factor with hexagonal shape. It was successfully used to compute a specific all loop four-point function for the first time. However, it seems that new developments are needed to understand the five-point function and other kinds of finite size corrections. In this talk, after a long review of the hexagonalization procedure, I will explain the five-point calculation at weak coupling and its difficulties.