This lab confronts common misconceptions about diffusion using engaging simulated molecular-level experiments. The lab first focuses on how individual molecules move under different conditions. It then sets up a fun experiment that allows students to explore whether nerve cells could use diffusion to move materials from the cell body to the synapses at the tips of their axons. Students run races in axons of different lengths and record how long it takes for "peptide" molecules to diffuse down their length. A new concluding exercise explores diffusion in plant leaves, asking whether CO₂ molecules that start among high concentrations of other CO₂ molecules move faster than CO₂ molecules that start among high concentrations of water molecules. By the end of the lab, students not only discover the need for cellular and organ level transport mechanisms, but also overcome some commonly held misconceptions (see our Publications page for details).