Between March and November 1868, while Darwin was researching his book The Expression of the Emotions in Man and Animals, he showed a succession of visitors a set of photographs of human faces, some with the muscles artificially contracted by electric probes, and asked them what emotion they thought the photographs conveyed. Darwin's research has striking parallels with contemporary facial recognition experiments. We have recreated Darwin's expression experiment online, using 21st century techniques to study many of the same problems that Darwin was interested in, using the same photographs Darwin used more than 100 years ago. Try the emotion experiment for yourself.