  We investigate the morphological, dynamical, and evolutionary properties of
the internetwork and network fine structure of the quiet sun at disk centre.
The analysis is based on a $\sim$6 h time sequence of narrow-band filtergrams
centred on the inner-wing \Ca II K$_{\rm 2v}$ reversal at 393.3 nm. The results
for the internetwork are related to predictions derived from numerical
simulations of the quiet sun. The average evolutionary time scale of the
internetwork in our observations is 52 sec. Internetwork grains show a tendency
to appear on a mesh-like pattern with a mean cell size of $\sim$4-5 arcsec.
Based on this size and the spatial organisation of the mesh we speculate that
this pattern is related to the existence of photospheric downdrafts as
predicted by convection simulations. The image segmentation shows that typical
sizes of both network and internetwork grains are in the order of 1.6 arcs.
