Boiling is the most efficient mechanism of heat transfer and is therefore applied in many technical systems for thermal energy conversion and transportation, for heating and cooling devices, and manufacturing processes. The design of these technical systems and their thermal control during operation demand qualified correlations to predict boiling heat transfer which are in spite of about six decades of research more or less only of empirical and semi-empirical nature. These correlations are limited to certain fluids, combinations of heater configurations and clearly defined ranges of liquid states for which they are developed. Boiling is characterized by its very complex behaviour, it consists of sequences of non-linear interacting events and therefore, up to now, its physics is not well understood. Results of recent studies in M G E are in contradiction to the prediction of most heat transfer correlations, and more general to the picture that exists from boiling. Microgravity permits the study of the real physics of boiling not masked by buoyancy convection. Under pool boiling and M G conditions the heat transfer and the related bubble dynamics are not influenced by external forces. In this case, the dynamics of the boiling process itself determines the heat transfer.