What is the perfect age?

This year, Gen-Xers are turning 50 and Baby Boomers are turning 70 -- two generations that are redefining what we think about age. So then at what age are we the happiest? Is there such a thing as the perfect age?

What is the perfect age? One magic number that makes us the happiest we'll be in our lives? We explore this question, from a 100-year-old who has defied conventions of age by going to work every day to patients who defy age by going under the knife to researchers who have poured years into figuring it out.