I often find that really simple visual aids are all that are needed to make otherwise quite complex concepts spring to life in the students’ minds. For example, a balloon inside a cardboard box to represent the protoplast inside the cell wall of a plant cell (particularly useful when teaching plasmolysis), pipe cleaners as polysaccharide chains or for demonstrating protein structure, and drawing pins stuck in ping-pong balls as viruses or cell-surface antigens.