The positive mental health effects of nature exposure in urban environments are well known, and the literature on the subject is growing fast. However, many previous studies have relied only on cross-sectional data that offer coarse measurements of the phenomenon. Writing in BioScience, Dr. Andrea Mechelli of King's College London and his colleagues describe a new approach: the Urban Mind smartphone app. By collecting data several times daily, the app provides real-time information on both the environment and the subjective well-being of its users. Through this approach, Mechelli and his colleagues were able to quantify nature's effects on human well-being with previously unseen accuracy and timeliness. Dr. Mechelli joins us in this episode of BioScience Talks to discuss these findings and to explain the next steps for Urban Mind.