This year's Nobel Prize for Medicine has gone to Dr. Robert G. Edwards, an English biologist who co-developed in vitro fertilization, the revolutionary process that has allowed millions of infertile couples to have babies. It's been thirty-one years since the first test tube baby was born. We take a look at how the world has changed since then with Robin Marantz Henig, author of "Pandora's Baby: How the First Test Tube Babies Sparked the Reproductive Revolution."

All this week we’re talking with our friends from Scientific American about endings: in nature, culture and science. For most of human history the clearest, most black and white ending in our lives was death. However, in recent decades, life support technology has made death a gray area, leading to right-to-life debates, as in the case of Terri Schiavo. But the question of when someone is dead becomes especially important when dealing with the process of organ donation.

We asked you, our listeners: If you are are an organ donor, what made you agree to it? If not, what's your reason against it? Let us know in the comments or call 877-8-MY-TAKE and we'll play the responses on the air.

We're looking at whether adulthood is arriving later in life, while adolescence gets longer. The New York Times Magazine looks at the issue this weekend. And we're asking: When did adulthood arrive for you? Complete this sentence: You know you're an adult when... Maybe it's graduating college? Moving out from your parents' house? Getting married? Let us know what it was for you.