With light, you can make some pathetic attempt to preserve it, to take a picture of it. Or like Monet you can paint a cathedral in various hours of the day. He knew what he was doing—the cathedral was only a ruse, a trap for capturing the rays of light. But with smells, no such tricks are available to us, there is no film or recording device, no

Scent is the only sense that is directly linked to the memory and emotional learning centers of the brain, says  Rachel Herz , a neuroscientist at Brown University and an expert on the psychological science of smell.