Heat-of-mixing calorimetry has been the starting point of a long dedication of the author to chemical thermodynamics as applied to different fields of theoretical as well as practical interests. From the heat of mixing measured at room temperature and normal pressure to heat capacities and mechanical coefficients measured over extended ranges of temperatures and pressures, from fluids to polymers, several milestones mark a passionate quest for a better understanding of the thermodynamics of molecular interactions in fluid mixtures and of phase changes in polymers.