Timeline of major events in the Orion region. The left column indicates the rough timing for each event. The middle column shows a schematic of the Orion region over time (viewed from the Galactic plane looking down toward Orion). The right most columns indicate the 2D and 3D data sets that support the timing and schematic of each event. “Gas 3D Velocities” refers to data from G21, “Stellar 3D Velocities” refers to our measurements of OBP-B1 and those of S21, and “3D dust” refers to the map from L20.