Natural or synthetic amphiphilic molecules in solutions can self-assemble to form variably-scaled structures such as micelles, discs, vesicles, tubes and fibers. Minor changes in the conformation and characteristics of amphiphiles can greatly adjust the packing parameters (P = v/a₀l₀) and, in turn, the microstructures and the macroscopic properties of self-assembled systems, i.e., viscosity and elasticity, in some cases leading to a phase transition of spontaneous aggregates. This review focuses on how to controllably tune the phase transition of aggregates by changing the external conditions, e.g., pH, temperature, light, and ionic strength. Recent progress in the phase transition of assembled structures induced by external stimuli is summarized. We do not attempt a comprehensive description of studies reported in the literature, but rather focus on those advances that come from our laboratory, which aim to give a comprehensive understanding of stimuli-responsive intelligent systems, including the transition process, transition mechanism and applications, and thus to provide a guideline for the preparation of smart systems and practical applications.