If 2019 was &;an Adornian year&; because of the 50th anniversary of the untimely death of Theodor W. Adorno in August 1969, 2020 will also be &;an Adornian year&; because of the 50th anniversary of the posthumous publication of Adorno&;s great but unfinished masterpiece Aesthetic Theory, edited by Gretel Adorno and Rolf Tiedemann and first published by Suhrkamp in 1970. Adorno&;s intellectual legacy is still alive today and indeed important for the conceptual tools as it still provides to develop a critical, active and negative (instead than acritical, passive and affirmative) relationship with the real. In the vast and complex corpus of Adorno&;s entire philosophical oeuvre, his aesthetic theory deserves an especially closed and renewed attention today for the variety of intellectual provocations that are still richly offered to us in order to critically understand our age. As Adorno writes in Aesthetic Theory, &;the aesthetic image is a protest against nature&;s fear that it will dissipate into the chaos. The aesthetic unity of the multiplicitous appears as though it had done no violence but had been chosen by the multiplicitous itself. It is thus that unity-today as real as ever was, the diremption-crosses over into reconciliation. [&;] In artworks, spirit is no longer the old enemy of nature. Assuaged, spirit reconciles. [&;] Reconciliation is the comportment of artworks by which they become conscious of the nonidentical. Spirit does not identify the nonidentical: it is identified with it. By pursuing its own identity with itself, art assimilates itself with the nonidentical: this is the contemporary stage of development of art&;s mimetic essence&;. This makes clear and explicit the continuity and affinity between the philosophical project of Aesthetic Theory and that of other fundamental works of Adorno like Dialectic of Enlightenment (with Max Horkheimer) and Negative Dialectics. And this also immediately shows the complexity of Adorno&;s concept of the aesthetic, connected to (but also not reducible to) the artistic, and related to other key-notions of his philosophy like &;mimesis,&; &;nature,&; &;spirit,&; &;history,&; &;semblance,&; &;beauty,&; the &;non-identical&; and the &;non-conceptual.&; In this volume, an international collection of outstanding scholars with different backgrounds, but united by a common interest in Adorno&;s aesthetics, will investigate &;the aging&; of his Aesthetic Theory 50 years later: its main concepts, its open questions, its relation with the aesthetic theories of other critical theorists and also with different traditions of 20th-century thought, its origins and legacy, and finally its unique way of representing today an incomparable source of inspiration to inquire into cultural phenomena of our time.