TREE (Transitions from Education to Employment) is a multi-disciplinary longitudinal large-scale survey providing high-quality longitudinal data on educational and occupational pathways in Switzerland for the use within the scientific community at large. The source of the data is a multi-cohort panel study of school leavers who are first surveyed at the end of compulsory school at the age of approximately 15 to 16 years. The first TREE cohort (TREE1) has been launched in 2000 and draws on a large national (compulsory) school leavers’ sample (N>6,000) tested and surveyed on the occasion of Switzerland’s then first-time participation in PISA. Since then, the sample has been followed up by means of 10 panel waves, the most recent one conducted in 2019/20. Further panel waves are planned at five-years intervals. Data on TREE1 respondents thus span a period of over 20 years, from early adolescence up to middle-age. The study thus has gradually grown into a full-blown life course survey. Over the years and across a wide range of academic disciplines (e.g. sociology, economics, psychology, educational and health sciences), TREE1 has become an invaluable database for research on pathways and transitions of adolescents and (young) adults. The TREE panel survey is to be found among Switzerland’s most widely used data infrastructures in the social sciences. The second TREE panel study (TREE2) covers a comparable population of school leavers who left compulsory education in 2016. As its baseline survey, it draws on a national large-scale assessment of mathematics skills. Much like TREE1, the TREE2 sample has been re-surveyed at yearly intervals from 2017 to 2022. Further panel waves will be conducted at multi-annual intervals, with the objective to replicate, as closely as possible, TREE1’s panel design. For more detail and publications see study website www.tree.unibe.ch