Time series showing the formation of an OPU in AR 11967. The individual columns show the observables of the OPU at different times, from 10:00 UT on 4 February 2014 to 1:10 UT on 5 February 2014. From top to bottom:I_c, B, B_LOS, γ, and v_LOS. All panels have a FOV of $38\stackrel{″}{.}4\times 25\stackrel{″}{.}6$. The magnetic feature that evolves into an OPU (and the OPU itself) is indicated by the red contours. This OPU forms by emerging in a plage region. We show the magnetic field and the velocity at τ = 1. The arrows in the top row point towards disk centre.