The late nineteenth-century vision of the philosopher presented in scholarship, fiction and monumental sculpture as a champion in the long fight between middle ages and Renaissance, reaction and progress, repression and freedom of thought, is undoubtedly at the root of Warburg’s Brunian interest which harks back to the 1910s. He became acquainted with Bruno through the Spaccio della Bestia, in which the philosopher endeavors to reform the imagery of the pre-modern sky. It is only in 1928-29, however, that this interest began to take the shape of an obsession.
In Warburg's correspondence the first traces go back to November 1928 when he invites Leonardo Olschki to give a lecture on Bruno. He wants him to talk about the function of classical mythology in Bruno's thought as he hoped that it might demonstrate a link between pagan image-based thought and modern symbol-based thought. For him Bruno is the pivotal thinker of the 16th century, an 'antenna', a receptor of European thought.
Parts of Warburg's last Italian trip in 1928-29 resemble a Brunian pilgimage that took him to Nola as well as to San Domenico maggiore - the Neapolitan Dominican monastery and church where Bruno was educated and from which he fled. Warburg also met Brunian scholars, most notably Giovanni Gentile, then editor of Bruno’s complete works. His Italian diary frequently mentions his 'incredibly difficult Giordano Bruno studies', which are gripping, surprising, but proceeding only slowly.
By the time of his return to Hamburg in July 1929 he felt he had reached a crossroad, '…where the attempt by the historian of pure thought meets the attempt by the historian of pure un-reason' in Giordano Bruno. Bruno's 'strange ambivalence' has become clear to him only now; he wants to give a lecture on Bruno as thinker in images; and he adds that without Gertrud Bing's assistance he would never have been able to proceed with his research, the result of which is the 'kulturwissenschaftlicher TypenAtlas’.  Thus Warburg's interest in Bruno relates directly to his attempt at developing a new method of working with images. In Bruno's work Warburg had identified a mode of thought which revealed the same energizing form, and the same tension of energies, that he had discovered in works of art and attempted to study in his unfinished Mnemosyne Bilderatlas.
Death prevented Warburg from completing his study on Bruno. The remains are sparse notes in his Italian diary - the so-called Library diary which he took to Italy with him - as well as a folder now kept in the archive entitled `Giordano Bruno' which contains about 40 leaves of notes and sketches in Warburg familiar handwriting. In the course of October 1929 he pencilled two tentative titles for his forthcoming essay: the first reads: Aesthetik als logische Orientierung bei Giordano Bruno; the second, re-elaborated after discussions with Edgar Wind and Gertrud Bing has become: Perseus, oder Energetische Aesthetik als logische Funktion im Geschäfte der Orientierung bei Giordano Bruno.
After Warburg's death in October 1929 and the migration of the Institute to London in 1933, Brunian studies at the Warburg Institute took a very different direction thanks to the research of Frances Yates (1899-1981).
 See Giovanni Gentile preface to the Bibliografia Bruniana, as well as Luigi Firpo’s introduction to the second edition of the Bibliografia Bruniana, Firenze 1958, pp. 13f.
 Letter to Karl Vossler, 12 October 1929.
 Nicholas Mann , 'Denkenergetische Inversion: Aby Warburg and Giordano Bruno', Publications of the English Goethe Society, 72, 2003, pp. 25-37. The first mention of Giordano Bruno in Warburg's correspondence goes back to 23 July 1915 and is related to the Spaccio della Bestia.
 For an overview of Bruno’s fortuna critica in the 19th century see Eugenio Canone introduction to the volume Bruno Redivivus. Momenti della fortuna di Giordano Bruno nel XIX secolo, a c. di E. Canone, Pisa 1998, pp. xi-xlv.
 Berggren, Lars, L'ombra dei grandi : monumenti e politica monumentale a Roma (1870-1895), Roma 1996, p. 123.
 Pietro Balan. Di Giordano Bruno e dei meriti di lui ad un monumento : saggio storico popolare. Bologna 1888.http://warburg.sas.ac.uk/mnemosyne/Bruno/pdf/1802286610.pdf
 Dialoghetti familiari tra un imbianchino e riquadratore di stanze fiorentino ed un signore romano sopra la vera storia di Giordano Bruno. Roma 1889. Contrarily to the author’s assertion the controversies raging around the monument had little echo outside Italy .
 See e.g. Luigi. Barbieri. Giordano Bruno e il suo monumento : conferenza tenuta nella sede dell' Associazione operaia Maria Immacolata, Napoli 1889, p. 7: ‘… io vedo una sfida sacrilega al Papato, un insulto alla Religione cattolica che segna la decadenza della Italia moderna e il principio di una nuova barbarie ’
 See e.g. Romeo Manzoni, La mente di Giordano Bruno, Locarno [s.d.], p. 6.
 C. E. Constance E. Plumptre. Giordano Bruno : a tale of the sixteenth century , London 1884; Leopold Schefer,Gottliche Komodie in Rom , Milan 1904.
 Filonomo. Scotino. Giordano Bruno : scena drammatica, Napoli 1870; Philipp Holitscher, Giordano Bruno : Historisches Drama in 5 Abteilungen; Stuttgart 1898; David Levi, Giordano Bruno, o, Le lotte del pensiero : dramma in cinque atti, Roma 1889; Otto Borngraber, Giordano Bruno : Das neue Jahrhundert. Eine Tragödie und Ouverture zur neuen Zeit, Leipzig 1901; Jose Fola Igurbide, Giordano Bruno : drama en cinco actos divididos en quince cuadros , Barcelona 1912; E. G. Erwin Guido Kolbenheyer, Heroische Leidenschaften : Die Tragödie des Giordano Bruno in drei Teilen. München 1929.
 Adelelmo Bartolucci, Giordano Bruno, Santarcangelo 1889; Charles Clair, Giordano Bruno ou le chevalier errant de la philosophie, Paris 1925.
 See L'ombra (as in n. 5), pp. 175-6, the medallions around the monument include the figures of Hus, Wycliffe, Servet, Paleario, Vanini, Ramus, Campanella and Sarpi.
 Tagebuch der Kulturwissenschaftlichen Bibliothek Warburg...; herausgegeben von Karen Michels und Charlotte Schoell-Glass, Berlin 2001, p. 375.  Letter to Fritz Saxl dated13 December 1928  Warburg Institute Archive, III. 121. 1.1