In the past decades, metal-organic frameworks (MOFs) have attracted considerable interest not only for their intrinsic aesthetic appeal but also their wide potential applications. The most distinctive feature of MOFs is their flexibility, which makes them exhibit a much larger magnitude of responses toward external stimuli than traditional materials. In addition, the stimuli usually have a huge impact on the MOFs' performances. A fundamental understanding of the structure evolution process under external stimuli is critical to reveal the structure-property relationships in MOFs. In this feature article, we tried to summarize how the crystal structure changes toward external stimuli, such as guest insertion, temperature, pressure, electric field, and light.