The space missions Yohkoh, SOHO and TRACE, together with complementary ground-based instrumentation, have in recent years given usa wealth of new results on the Sun, which are not readily available or digestible for the non-specialist. They are presented here in an organised, tutorial fashion by leading astrophysicists who gathered to observe the total eclipse of 11 August 1999 in Bucharest. Subjects covered range from the deep solar interior to the extended corona, with an emphasis on the diagnostic and on the physical interpretation of the spectacular phenomena represented by solar activity. Readership: Primarily graduate students. Senior scientists will appreciate the comprehensive update of solar physics. Amateur astronomers having an adequate knowledge of physics will also enjoy the book.