3D visualization of the magnetic field configuration of the He I 1083 nm emission event in our MURaM simulation. The greyscale background shows the vertical magnetic field in the photosphere (white: positive; black: negative), just above the continuum formation height. The red surface displays the height of optical depth unity z(τ = 1) for the vertically emergent intensity at Δv = −18 km s⁻¹ for the He I 1083 nm line, corresponding to the blue wing images in Fig. 10. This height tends to lie below the height for which we display the magnetic field, and is above it only in some locations, appearing as steeply-sided columns. The magnetic field lines thread the emitting region of the He I 1083 nm brightening, and their color indicates the local temperature. Figure made with VAPOR (Li et al. 2019).