TREE (Transitions from Education to Employment) is a Swiss nationwide longitudinal study that follows two cohorts of compulsory school leavers throughout their transitions from education to employment and middle adulthood. To date, the first cohort survey (initial N=6,343) based on the Swiss PISA 2000 sample has covered a 14-year period from age 15 to 29 (nine follow-up surveys). The second cohort survey started in 2016 (with one follow-up survey in spring 2017 so far; initial N=9,762) and is based on a large national representative sample of students (N=22,378) who sat a mathematics test at the end of the ninth grade (approximately 15 years old). TREE is designed to provide comprehensive data for the analysis of post-compulsory education, employment and other pathways (e.g. family and household situation, income/financial situation, critical life events, social integration and participation, psycho-social personal characteristics, health and wellbeing). As a social science infrastructure project of national and international importance, its data is freely available to the scientific community at large. This paper provides an overview of the TREE study with a specific focus on the latest data release (September 2016) for the first TREE cohort.