  The origin of the slow solar wind is still an open issue. One possibility
that has been suggested is that upflows at the edge of an active region can
contribute to the slow solar wind.
  We aim to explain how the plasma upflows are generated, which mechanisms are
responsible for them, and what the upflow region topology looks like.
  We investigated an upflow region using imaging data with the unprecedented
temporal (3s) and spatial (2 pixels = 236km) resolution that were obtained on
30 March 2022 with the 174{\AA} of the Extreme-Ultraviolet Imager (EUI)/High
Resolution Imager (HRI) on board Solar Orbiter. During this time, the EUI and
Earth-orbiting satellites (Solar Dynamics Observatory, Hinode, and the
Interface Region Imaging Spectrograph, IRIS) were located in quadrature (92
degrees), which provides a stereoscopic view with high resolution. We used the
Hinode/EIS (Fe XII) spectroscopic data to find coronal upflow regions in the
active region. The IRIS slit-jaw imager provides a high-resolution view of the
transition region and chromosphere.
  For the first time, we have data that provide a quadrature view of a coronal
upflow region with high spatial resolution. We found extended loops rooted in a
coronal upflow region. Plasma upflows at the footpoints of extended loops
determined spectroscopically through the Doppler shift are similar to the
apparent upward motions seen through imaging in quadrature. The dynamics of
small-scale structures in the upflow region can be used to identify two
mechanisms of the plasma upflow: Mechanism I is reconnection of the hot coronal
loops with open magnetic field lines in the solar corona, and mechanism II is
reconnection of the small chromospheric loops with open magnetic field lines in
the chromosphere or transition region. We identified the locations in which
mechanisms I and II work.
