  We review our strategy to study hadron interactions from lattice QCD using
newly proposed potential method. We first explain our strategy in the case of
nuclear potentials and its application to nuclear physics. We then discuss the
origin of the repulsive core, by adding strange quarks to the system. We also
explore a possibility for H-dibaryon to exist in flavor SU(3) limit of lattice
QCD. We conclude the paper with an application of our strategy to investigate
the maximum mass of neutron stars.
