Consideration of mass transfer and mass loss processes allows the explanation of the existence of well determined groups of binaries, such as Algols, cataclysmic variables, massive and low masa X ray binaries. The characteristics of these groups are briefly outlined, and evolutionary scenarios are discussed. The importance of detailed observations for advances in evolutionary computations are stressed. It isargued that, although the linka between the mentionned groups of binaries and their progenitors is rather well known, the situation is completely different if the detailed evolutionary history for a given system is required.
The final dynamical evolution of a cluster is strongly influenced by the removal of the parent gas cloud after the star formation process in the region has stopped. The knowledge of a number of essential physical parameters of young open clusters and associations, such as the mass and velocity distribution of the stars and the gas as a function of position in the cluster, is of vital importance for the construction of detailed dynamical models of these regions. In this context, NGC 2244 has been selected for an observational study. We present our first results, including progress made on membership determination and detection of Hα emission B-type
stars .