This publication is composed of all the slides Frido Troost (1960-2013) used for his classes at the Gerrit Rietveld Academie. Troost, art historian by trade, was a pioneer in collecting photography of all sorts. In his store ‘Institute for Concrete Matter’ many types of photography were represented, varying from daguerreotypes to albumin prints, stereo photos to family albums. The images in this book come from all kinds of sources: paintings, advertisements, erotica, art objects, portraits, etc. They form a new collection that represents Frido Troosts associative way of looking. The slides are presented in blocks of nine, in the same construct as Frido Troost gave his classes, a non-hierarchal set up that invites the viewer to link the images freely. A controversial mix that covers a big part of the history of photography.