<strong class="journal-contentHeaderColor">Abstract.</strong> Ozone formation is nonlinear, and results from the photochemical oxidation of methane and non-methane hydrocarbons (NMHCs) in the presence of nitrogen oxide (NO_x=NO+NO₂). Previous studies showed that O₃ short- and long-term trends are nonlinearly controlled by near-surface anthropogenic emissions of carbon monoxide (CO), volatile organic compounds (VOCs), and nitrogen oxides. In this review article, we investigate tropospheric ozone spatial variability and trends from 2005 to 2019 and relate those to ozone precursors on global and regional scales. We also investigate the spatiotemporal characteristics of the ozone formation regime in relation to ozone chemical sources and sinks. Our analysis is based on remote sensing products of the Tropospheric Column of Ozone (TrC-O₃) and its precursors, nitrogen dioxide (TrC-NO₂), formaldehyde (TrC-HCHO), and total column of CO (TC-CO) as well as ozonesonde data and model simulations. Our results indicate a complex relationship between tropospheric ozone column levels, surface ozone levels, and ozone precursors. While the increasing trends of near-surface ozone concentrations can largely be explained by variations in VOC and NO_x concentration under different regimes, TrC-O₃ may also be affected by other variables such as tropopause height. Decreasing trends in TrC-NO₂ have varying effects on the TrC-O₃, which is related to the different local chemistry in each region. The concomitant increase or decrease in TrC-O₃ and TrC-NO₂ over the eastern US, and central Europe is due to dominant NO-sensitive conditions resulting from the strict measures to control NO_x emissions over the last two decades. The decreasing trends of TrC-NO₂ but increasing trends of TrC-O₃ in some regions in the central US and parts of eastern Asia are due to high NO_x conditions leading to VOC sensitivity in these regions. We also shed light on the contribution of NO_x lightning and soil NO and nitrous acid (HONO) emissions to trends of tropospheric ozone on regional and global scales.