  We explore in detail oscillations of the solar $^7$Be neutrinos in the matter
of the Earth. The depth of oscillations is about $(0.1 - 0.2)\%$ and the length
$\approx 30$ km. The period of the oscillatory modulations in the energy scale
is comparable with the width of the line determined by the temperature in the
center of the Sun. The latter means that depending on the length of trajectory
(nadir angle) one obtains different degree of averaging of oscillations.
Exploring these oscillations it is possible to measure the width of the $^7$Be
line and therefore the temperature of the Sun, determine precisely $\Delta
m^2_{21}$, perform tomography of the Earth, in particular, measure the
deviation of its form from sphere, and detect small structures. Studies of the
Be neutrinos open up a possibility to test quantum mechanics of neutrino
oscillations and search for the sterile neutrinos. Accuracy of these
measurements with future scintillator (or scintillator uploaded) detectors of
the $\sim 100$ kton mass scale is estimated.
