In this 24-minute conference talk from the Fields-CFI Conference on Optimal Stopping and Its Applications in Finance and Insurance, Yuqiong Wang from the University of Michigan, Ann Arbor explores stopping problems with an unknown state. Delivered on May 13, 2025, at the Fields Institute, the presentation delves into mathematical frameworks for decision-making under uncertainty when the underlying state is not fully observable. Learn about theoretical approaches and practical applications in finance and insurance for optimal stopping strategies when working with incomplete information. For more detailed information about the talk's content, refer to the abstract available on the Fields Institute website.