Project Summary/Abstract Exposure to greenspace, broadly defined as various forms of vegetation, has been shown to confer numerous health benefits. Specifically, reduction of the mental health impact of stressful life events, improving cognitive functioning, and decreasing symptoms associated with attention deficit hyperactivity disorder (ADHD), and other behavioral problems. Increased exposure to greenspace has also been associated with better sleep quality and longer sleep duration. The evidence base of the positive impact of green space on health has proliferated to such an extent that in 2015, the United Nations adopted the exposure to green space as a sustainable development goal, with target 11.7 stating “By 2030, provide universal access to safe, inclusive and accessible, green and public spaces, particularly for women and children, older persons and persons with disabilities. Notwithstanding the health benefits of greenspace on health, few studies have explicitly examined the relationship between greenspace, sleep and mental health, or have fully disentangled underlying mechanisms accounting for the association between these critical pillars of overall health and well-being. Moreover, most studies examining the relationship between greenspace and health outcomes have focused on measures of greenspace of where one lives rather than where one actually spends time within a 24-hour period. By accounting for where individuals actually spend time, we can examine time spent in greenspace (i.e., utilization) which can better capture the association between greenspace and health beyond measures of proximity or accessibility based on where one lives. We hope to address the gap in the literature exploring green space, sleep and mental health through the following specific aims: Aim 1. Sleep and greenspace. To determine how green space utilization (GPS-derived measures of daily activity and environmental features) is related to sleep (duration, timing, regularity) in children. Aim 2. Mental health, greenspace and sleep. To determine whether greenspace utilization is associated with mental health and wellbeing via sleep behaviors. Exploratory Aim 3. Contextual factors influencing sleep, mental health, greenspace. To evaluate how the associations among greenspace, sleep, mental health, and wellbeing vary as a function of contextual factors such as socioeconomic status. Although the World Health Organization recognizes greenspace access as a structural intervention for health, more information is needed about the impact of greenspace utilization to improve sleep, mental health and wellbeing of children.