A team of researchers from the Moscow Institute of Physics and Technology, and Aarhus University in Denmark has developed an algorithm for predicting the effect of an external electromagnetic field on the state of complex molecules. The algorithm, which is based on a theory developed earlier by the same team, predicts tunneling ionization rates of molecules. This refers to the probability that an electron will bypass the potential barrier and escape from its parent molecule. The new algorithm, presented in a paper in the Journal of Chemical Physics, enables researchers to look inside large polyatomic molecules, observe and potentially control electron motion therein.