  We present results of a high-resolution zoom cosmological simulation of the
evolution of a low-mass galaxy with a maximum velocity of V=100 km/s at z=0,
using the initial conditions from the AGORA project (Kim et al. 2014). The
final disc-dominated galaxy is consistent with local disc scaling relations,
such as the stellar-to-halo mass relation and the baryonic Tully-Fisher. The
galaxy evolves from a compact, dispersion-dominated galaxy into a
rotation-dominated but dynamically hot disc in about 0.5 Gyr (from z=1.4 to
z=1.2). The disc dynamically cools down for the following 7 Gyr, as the gas
velocity dispersion decreases over time, in agreement with observations. The
primary cause of this slow evolution of velocity dispersion in this low-mass
galaxy is stellar feedback. It is related to the decline in gas fraction, and
to the associated gravitational disk instability, as the disc slowly settles
from a global Toomre Q>1 turbulent disc to a marginally unstable disc (Q=1).
