This book is unique, since it reveals the outstanding personality underlying Majorana's notes. An extraordinary mixture of mathematical command, physics intuition and creative thought makes the Notes enjoyable for physicists of every discipline. The Notes are interesting for both graduate students and theoretical physics experts. In fact, the contents range from applied physics models, thorough fundamental atomic physics, to advanced group theory. The Notes have never been published and here they appear in the same format as organized by Ettore Majorana. The style is plain, proposed solutions to physics problems are original. These notes are intended as a series of fundamental physics themes treated by Ettore Majorana during the first "burning years" of the Panisperna Group, as the new deal of physics started in Rome around Enrico Fermi.