The output of the observational parameterization will be combined into a database which we will use to address a number of different theoretsical problems. Our knowledge of these objects is very limited because of their short history hence the scope for theoretical advances is widespread. We will be working actively in the testing and development of models, using brown dwarfs to study our galaxy, the determination of the sub-stellar IMF and finally understanding the population and properties of objects in the 300-700K regime e.g. objects similar to giant planets of the solar system. Some of this work has already begun especially on the IMF and comparison of models but the majority will come in the last part of the IPERCOOL collaboration.