  $VO_2$ undergoes the insulator-metal transition (IMT) and monoclinic-rutile
structural phase transition (SPT) near $67^oC$. The IMT switching has many
applications. However, there is an unresolved issue whether the IMT is a Mott
transition or a Peierls transition. This complication is caused by metal and
insulator coexistence, which is an inherent property of the IMT region. Thus,
the acquired data in the IMT region are averaged over the two phases in many
experiments. We overcome the issue by probing the electronic state of the
monoclinic structure and by introducing a model that accounts for the
coexisting phases. We reveal the Mott IMT in the non-distorted monoclinic
nanodomain between $55-63^oC$, and the distortion-assisted SPT above $60^oC$.
