Bottom-up Approach in Supersymmetric Models

We present a bottom-up approach to the question of supersymmetry breaking in the MSSM. Starting with the experimentally measurable low energy supersymmetry breaking parameters which can take any values consistent with present experimental constraints, we evolve them up to an arbitrary high energy scale. Approximate analytical expressions for such an evolution, valid for low and moderate values of $\tan\beta$, are presented. We then discuss qualitative properties of the high energy parameter space and in particular, identify the conditions on the low energy spectrum which are necessary for the parameters at high energy scale to satisfy simple regular pattern such as universality or partial universality.