We have investigated, both experimentally and theoretically, the aggregation of ABA amphiphilic triblock copolymers in dilute solution. We observed a number of complex architectures having toroidal and network structures, including some novel ones. The computational analyses of these systems offer some insight into the origins of the self-assembly of these amphiphiles. The results we obtained using real-space self-consistent field theory reveal that the formation of network and toroidal structures from the block copolymers occurs as the result of the breaking of "inhomogeneous vesicles"; the observed polymorphism results from the existence of multiple metastable states.