The computational science principles coupled with statistical mechanical concepts and readily available computer power allows a detailed understanding of atomic and molecular scale phenomena, using increasingly realistic models. The simultaneous use of meso-scale and macro-scale methods opens multiscale simulation of complex processes yielding a key tool to assist process design. These simulation methods have also led to the development of new semi-theoretical equations of state that make it possible to introduce increased predictive power into the process simulators, and open the way for true product design methodologies. The scope of the experimental developments is also enhanced through the increased use of complementary data (calorimetry, spectroscopy, etc.) so as to ensure a coherent and complete picture of the microscopic fluid structure and macroscopic phase behavior.