TREE (Transitions from Education to Employment) is a prospective interdisciplinary multi-cohort panel survey following up on the (post-compulsory) education and employment trajectories of two large samples of Swiss compulsory school leavers. The first TREE cohort (TREE1) was launched in 2000, drawing on the sample tested on the occasion of Switzerland’s first-time participation in PISA ( Nt0 = 6,343, Nt10 in 2020 ≈ 3,900). 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 5 years intervals. To date, TREE1 respondents have reached an average age approaching 40 and have been surveyed for a period of over 20 years, spanning from early adolescence up to early middle age. Under a replication design allowing for cohort comparison, the second TREE cohort (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. Since then, the TREE2 sample ( Nt0 = 8,429, Nt6 in 2022 ≈ 4,500) has been re-surveyed six times at yearly intervals, up to the average age of 21. Further panel waves at 2–5 years intervals are planned. The present contribution includes a detailed description of TREE’s study and survey design as well as a synoptic summary of salient results from some of the several hundred publications that draw on the TREE data.