Recent cosmological observations suggest that a large fraction of the energy density of the universe has negative pressure. Quintessence, a slowly-varying, spatially inhomogeneous component, such as a scalar field evolving down a potential have been considered as a candidate for the ``missing energy''. The energy density of quintessence and matter density decrease at different rates as the universe expands. Hence, it seems that the initial condition has to be tremendously fine tuned to make two of them comparable today. We find that for a broad family of quintessence models, the cosmology is actually extremely insensitive to the initial conditions. The scalar field ``tracks'' a solution purely determined by the form of the potential. We also present the general conditions a model has to satisfy so that it exhibits this kind of ``tracking behavior''.