We discuss the physics of the mirror (shadow) world which is completel
y analogous to the visible one except that its 'weak' scale is larger
by one or two orders of magnitude than the weak scale in the standard
model. The mirror neutrinos can mix the ordinary ones through the Plan
ck scale induced higher order operators, which can help to reconcile t
he present neutrino puzzles that are the solar and atmospheric neutrin
o deficits, the recent LSND anomaly and the need in the similar to eV
mass neutrino as the hot dark matter. In particular, the oscillation o
f nu(e), into its mirror partner nu(e)' emerges with parameters natura
lly in the MSW range. The nucleosynthesis constraint on the extra ligh
t particle species can be fulfilled by assuming the asymmetric postinf
lationary reheating between the usual and mirror worlds. One implicati
on of our proposal is that bulk of the dark matter in the universe may
be a warm dark matter consisting of the keV range mirror neutrinos ra
ther than the conventional cold dark matter, while the mirror baryons
can also contribute as dissipative dark matter. Implications of the mi
rror Machos for microlensing experiments are also discussed.