Conceptual model of the formation of the Orion Complex, excluding Orion B and λ Ori. Black contours represent the molecular gas, red dots are the stars. The observer is located to the right of the image, direction indicated by the arrow. Left: early epoch of star formation in the filament. Middle: post supernova eruption, the filament begins to be split and compressed. Star formation in Orion C & D continues as they separate. Beginning of the compression of the gas in the direction of the filament, seeding the formation of the ONC. Right: The molecular gas in Orion C & D has been largely dissipated, as the stars inside them continue spherical expansion. The ONC becomes massive. L1641 becomes dense enough to begin forming stars.