  We survey some of our recent results on inverse problems for evolution
equations. The goal is to provide a unified approach to solve various types of
evolution equations. The inverse problems we consider consist in determining
unknown coefficients from boundary measurements by varying initial conditions.
Based on observability inequalities and a special choice of initial conditions,
we provide uniqueness and stability estimates for the recovery of volume and
boundary lower order coefficients in wave and heat equations. Some of the
results presented here are slightly improved from their original versions.
