  Dark energy is interpreted as the leftover of mostly canceled vacuum energy
due to the spontaneous mirror symmetry breaking (SMSB) at the electroweak phase
transition. Based on the newly proposed mirror-matter model (M$^3$), the
extended standard model with mirror matter (SM$^3$) is elaborated to provide a
consistent foundation for understanding dark energy, dark matter, baryogenesis,
and many other puzzles. New insights of Higgs, top quark, and lepton masses are
presented under SM$^3$ using staged quark condensation and four-fermion
interactions for SMSB. In particular, the nature and mass scales of neutrinos
are naturally explained under the new theory. The new cosmology model based on
SM$^3$ could potentially resolve more cosmic enigmas. The possible underlying
principles for SMSB and SM$^3$ of a maximally interacting, supersymmetric, and
mirrored world are also discussed.
