Each TBF is associated with an electronic state in which it evolves adiabatically. Nonadiabatic population transfer occurs via the coupling between TBFs on different electronic states mediated by the nonadiabatic couplings. The most characteristic feature of AIMS is the time-dependence of the size of the Gaussian basis. If a TBF encounters a region of high nonadiabaticity, it will spawn a new function onto the corresponding state. This function initially has an amplitude of zero but is fully coupled to the other TBFs in the simulation and ensures a smooth transfer of amplitude between the two coupled electronic states.