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 da-guerreotypes 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.