Large-scale long-term manipulative experiments have been effective in studying ecosystem responses to one or more drivers under a control condition. The warming experiment mimics the global warming by increasing either soil temperature or whole-ecosystem temperature to a certain degree. The warming experiment helps us understand the change of biogeochemical cycles and ecosystems functions in response to warming, and helps validate ecosystem models that can predict the future change under the warming condition. The warming experiment has been started since early 1990’s. The published literature indicates that ecosystem responses to long-term warming are more complex that we expected. For example, soil respiration will increase with warming without much surprise. However, the sensitivity of soil respiration to warming may change over time with the mechanism of acclimation and adaptation unknown. Furthermore, the components of photosynthesis, plant respiration, and microbial respiration in response differently to warming are unclear. The coupling of carbon and nitrogen cycles under warming is far from clear. The purpose of this Session is to bring scientists conducting the warming experiment worldwide together to address what we have learned from the warming experiment, what is unknown, and what is the future direction and challenge in conducting the warming experiment. We expect to conduct synthesis work across the sites and publish a special issue of journal papers following the Session.