Different by Design: Take a look at sexual progression from adulthood to old age. From sexual attraction to physical stamina, every angle is explored. Watch as identical twins are put to a real-life test of sexual attraction. And, thanks to some computer animation and unique endoscopic filming techniques, you'll see what goes on inside their bodies when they're aroused. Study the mechanics of intercourse using an MRI scanner and get a close-up look at the peaks and valleys of brain activity in the two sexes when processing emotion.