In this contribution we give a pedagogic introduction to the newly introduced adaptive interpolation method to prove in a simple and unified way replica formulas for Bayesian optimal inference problems. Many aspects of this method can already be explained at the level of the simple Curie-Weiss spin system. This provides a new method of solution for this model which does not appear to be known. We then generalize this analysis to a paradigmatic inference problem, namely rank-one matrix estimation, also refered to as the Wigner spike model in statistics. We give many pointers to the recent literature where the method has been succesfully applied.Keywords adaptive interpolation · Bayesian inference · replica formula · matrix estimation · Wigner spike model · Curie-Weiss model · spin systems 1 IntroductionThe replica method from statistical mechanics has been applied to Bayesian inference problems (e.g., coding, estimation) already two decades ago [1,2]. Rigorous proofs of the formulas for the mutual informations/entropies/free energies stemming from this method, have for a long time only been partial, consisting generally of one sided bounds [3,4,5,6,7,8,9,10]. It is only quite recently that there has been a surge of progress using various methods -namely spatial coupling [11,12,13,14,15], information theory [16], and rigorous versions of the cavity method [17,18,19]-to derive full proofs, but which are typically quite complicated. Recently we introduced [20] a powerful evolution of the Guerra-Toninelli [21,22,23] interpolation method -called adaptive interpolation-that allows to fully prove the replica formulas in a quite simple and unified way for Bayesian inference problems. In this contribution we give a pedagogic introduction to this new method.We first illustrate how the adaptive interpolation method allows to solve the well known Curie-Weiss model. For this model a simple version of the method contains most of the crucial ingredients. The present rigorous method of solution is new and perhaps simpler