Abstract
We discuss the interpretation of tunneling experiments on single molecules or semiconductor quantum dots weakly coupled to metallic electrodes. We identify the main features in the current-voltage curves and in the conductance using an extension of the theory of single charge tunneling. We analyze important quantities, such as the charging energy and the quasiparticle gap, providing simple rules to interpret the experiments. We discuss the limitations of the capacitance model to describe the system. We show that at a bias larger than the band-gap energy of the nanostructure the tunneling of both electrons and holes must be taken into account. We use self-consistent tight-binding calculations to illustrate these points and provide a comparison with recent experimental results on InAs nanocrystals