Neuroengineer Ed Boyden wants to know how the tiny biomolecules in our brains generate emotions, thoughts and feelings — and he wants to find the molecular changes that lead to disorders like epilepsy and Alzheimer's. Rather than magnify these invisible structures with a microscope, he wondered: What if we enlarge them so they are easier to see? Learn how the same polymers used to make baby diapers swell could be a key to better understanding our brains.