3-D instructional materials like objects, specimens, models and dioramas can help teach concepts that may otherwise be difficult. Models are modified replicas that can be larger, smaller, or show interior views of objects. They serve purposes like representing things too small or large to bring into the classroom, depicting the past or future, overcoming physical inaccessibility, and explaining processes. Common model types include solid models for recognizing external features, cross-section/cut-away models showing internal structures, construction models that can be assembled/disassembled, and working models indicating operations. Mock ups arrange devices to represent reality in a simplified way, focusing on certain features. Dioramas are 3D scenes meant to replicate reality against