The photographic heritage is composed of 850.000 original photographs, datable between 1840 and today, representing all the experimental photographic techniques attempted in the 19th and 20th centuries,  as well as works by important photographers including, Nadar, Adolphe Braun, Franz Hanfstaengl, the Brogi and the Alinari of Florence, the Andersons of Rome, Carlo Naya from Venice, Alfred Noack, Giorgio Sommer, Eugène Sévaistre, the Milanese Alessandro Duroni, Pompeo Pozzi, Luigi Sacchi, Giulio Rossi, Icilio Calzolari, Guigoni & Bossi,  Studio Ganzini, Leone Ricci, Varischi & Artico, Giuseppe Beltrami, Luca Comerio and Italo Pacchioni. Also, phototgraphers working throughout Europe and in various parts of the Ottoman Empire, China and Japan, such as Abdullah Frères, the Bonfils, Antonio and Felice Beato, James Robertson, the Bisson brothers, Édouard Denis Baldus, Henry Peach Robinson; Novecento photgraphers such as Emilio Sommariva, Antonio Paoletti, Mario Perotti, Mario Crimella, Dino Zani, Attilio Badodi, Elio Luxardo, Bruno Stefani, Claudio Emmer and Paolo Monti.

The various collections include such diverse subjects as the historic and artistic heritage of Milan and Lombardy, the urban and social history of Milan, portraits, journalism focused on various historic events, such as the Roman Republic of 1849, the Risorgimento and 1898 uprisings, Italian landscapes, views of European and world cities in the Ottoman Empire, China, India and Japan.

Of particular relevance are the Iconographic Collection, which provides testimony of Lombardy and Milan's artistic and historic heritage; the Beltrami Collection, dedicated mainly to the history of the city and the Sforza Castle; the Lamberto Vitali collection, put together by the first academic of Italian photography, which includes daguerreotypes, salt prints and important photographic series such as those by James Robertson on the war in Crimea in 1855; Eugene Sévaistre's albums on the storming of Gaeta and the revolt of Palermo in 1860 and views of Italy and other countries by the Bisson brothers and Édouard Denis Baldus.