Diary studies are a type of user research method in which participants are asked to record their thoughts, experiences, and behaviors over a period of time. This can be done using a physical diary or journal, or using a digital tool such as a mobile app or website. Diary studies are often used to study behaviors or activities that are difficult to observe directly, such as how people use a product or service in their daily lives. They can also provide insights into the emotional and psychological factors that influence user behavior, as participants are often more willing to share their personal thoughts and feelings in a diary than they would be in a face-to-face interview. Diary studies can be a valuable complement to other user research methods, providing a more in-depth and nuanced understanding of user behavior.