One of the most important problems in modern science is the origin of the Earth and formation of its shell. Modern views on the chemical composition of meteorites, planets and other bodies of the Solar System are pres­ented in this book. On the basis of recent achievements in cosmochemistry, the author, who is one of the leading scientists in the field of geochemistry, geophysics, de­ scribes the most probable processes that determined the chemical composition of the Earth in the remote past. Prof. George Voitkevich is also a winner of the Kar­pinsky Prize, which is given to a scientist for outstand­ing work in geology by the USSR Academy of Sciences.