The 20th century dared all kinds of upheavals, in all fields: in art, in life, in society, in political organization. The entire history of the 20th century confirms the diversity of uprisings and subsequent upheavals: violent and peaceful, individual and collective, humanistic or nihilistic. The "Century of Upheavals", as a necessary aid in the effort to understand our era, illuminates the events, currents and movements, persons and places that forged it. This dictionary, in the form of a time-shifted account of the 20th century, is not only a rediscovery of our time. It is a collective and synthetic work, as it has been written by historians, philosophers, novelists and essayists with sometimes radically different sensibilities, and derives its richness from their varied biased judgments. The material covers a wide range of subjects, from Picasso to the Beatles and from Greenpeace to May '68. The approximately 500 entries, written by more than 150 authors, are divided according to their content into five sections: - themes - movements - biographies - titles of works - locations and objects. The whole is structured on the relationships of the conceptual entries (which form the skeleton of the book) with their "satellites", biographies, movements, titles, locations and objects. Also, next to some entries, there are some pages, which are dedicated to topics that complement the entries. From the era of the historical "avant-garde" to the present day, from the pioneers of the turn of the century to Nelson Mandela, we find that to "do something" also means to want to "broaden the limits of the possible".