This document discusses three dimensional instructional materials and their use in teaching. It identifies different types of three dimensional materials including specimens and objects, models and mock ups, and other contrived experiences like aquariums and terrariums. Models and mock ups are described as recognizable imitations of real objects that are usually scaled down. Cautions are noted about using models, including potential misconceptions between real and contrived versions. The document also provides an activity for students to design and create their own masks.