(a) Objects that belong to the same category can be made of different materials. These vehicles are made of (from left to right): metal, plastic, and wood. (b) On the other hand, objects that belong to different categories can be made of the same material. Consider the fabric and glass examples. The scarves and the cat-shaped pillow are both made of fabric. Similarly, the frog and the crystal glasses are both made of glass. These images belong to the Flickr Materials Database (FMD) [Sharan et al., 2009], which consists of a diverse selection of surfaces in ten common material categories. We will use FMD in this paper to design image features and to evaluate material recognition systems.