Aided by brain scans, EEGs, slow motion video, gene-mapping and a host of new tools, scientists from diverse fields are digging into the underlying realities and causes of laughter. What is the difference between the laughter resulting from being tickled and the laughter at hearing a joke? The awkward laughter of being put on the spot versus the intellectual laughter of a great pun? Do animals laugh? Do computers laugh? How did laughter evolve in humans? Is laughter really the best medicine?