  Sunspots are the most spectacular manifestation of solar magnetism, yet, 99%
of the solar surface remains 'quiet' at any time of the solar cycle. The quiet
sun is not void of magnetic fields, though; they are organized at smaller
spatial scales and evolve relatively fast, which makes them difficult to
detect. Thus, although extensive quiet Sun magnetism would be a natural driver
to a uniform, steady heating of the outer solar atmosphere, it is not clear
what the physical processes involved would be due to lack of observational
evidence. We report the topology and dynamics of the magnetic field in very
quiet regions of the Sun from spectropolarimetric observations of the Hinode
satellite, showing a continuous injection of magnetic flux with a well
organized topology of Omega-loop from below the solar surface into the upper
layers. At first stages, when the loop travels across the photosphere, it has a
flattened (staple-like) geometry and a mean velocity ascent of $\sim3$ km/s.
When the loop crosses the minimum temperature region, the magnetic fields at
the footpoints become almost vertical and the loop topology ressembles a
potential field. The mean ascent velocity at chromospheric height is $\sim12$
km/s. The energy input rate of these small-scale loops in the lower boundary of
the chromosphere is (at least) of 1.4x10^6-2.2x10^7 erg cm-2 s-1. Our findings
provide empirical evidence for solar magnetism as a multi-scale system, in
which small-scale low-flux magnetism plays a crucial role, at least as
important as active regions, coupling different layers of the solar atmosphere
and being an important ingredient for chromospheric and coronal heating models.
