On May 23, 1989, Stefania Follini came out from a cave at Carlsbad, New Mexico. She hadn't seen the sun for eighteen and a half weeks. Stefania was in a research program, and the scientists in the program were studying body rhythms. In this experiment Stefania had spent 130days in a cave, 30 feet in depth.

    During her time in the cave, Stefania had been completely alone except for two white mice. Her living place had been very comfortable, but there had been nothing to tell her the time. She'd had no clocks or watches, no television or radio. There had been no natural light and the temperature had always been kept at 21℃.

    The results were very interesting. Stefania had been in the cave for over four months, but she thought she had been there for only two. Her body clock had changed. She hadn't kept to a 24-hour day, she had stayed awake for 20～25 hours and then had slept for 10 hours. She had eaten fewer meals and had lost 171bs in weight as a result! She had also become rather depressed.

    How had she spent her time in the cave? As part of the experiment she'd done some physical and mental tests. She'd recorded her daily activities and the results of the tests on a computer. This computer had been specially programmed for the project. Whenever she was free, she'd played cards, read books and listened to music. She'd also learned French from tapes.

    The experiment showed that our body clocks are affected by light and temperature. For example， the pattern of day and night makes us wake up and go to sleep. However, people are affected in different ways. Some people wake up naturally at 5:00 a.m., but others don't start to wake up till 9:00 or 10:00 a.m. This affects the whole daily rhythm. As a result the early risers are at their best in the late morning. The late risers, on the other hand, are tired during the day and only come to life in the afternoon or evening!

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    Several years ago, my parents, my wife, my son and I ate at one of those restaurants where the menu is written on a blackboard. After a wonderful dinner, the waiter set the check in the middle of the table. That's when it happened：my father did not reach for the check.

    Conversation continued. Finally I realized that I should pick up the check! After hundreds of restaurant meals with my parents, after a lifetime of thinking of my father as the one with dollars, it had all changed. I reached for the check, and my view of myself suddenly changed. I was an adult. I was no longer a kid (child).

Some people mark off (区分) their lives in years, I measure mine in small events. I didn't become a young man at a particular age, like 16, but rather when a kid who wandered in the streets called me "mister". These events in my life are called "milestones"(里程碑).

    There have been other milestones. The cops (policemen) of my youth always seemed big, even huge, and of course they were older than I was. Then one day they were suddenly neither. The day came when I suddenly realized that all the football players in the game I was watching were younger than I was. They were just big kids. With that milestone gone was the dream that someday, maybe I, too, could be a football player. Without ever having reached the hill, I was over it.

    I never thought that I would fall asleep in front of the TV set as my father did. Now it's what I do best. I never thought that I would go to the beach and not swim, yet I spent all of August at the shore and never once went into the ocean. I never thought that I would appreciate opera, but now the combination of voice and orchestra attracts me. I never thought that I would prefer to stay home in the evenings, but now I find myself passing up parties. I used to think that people who watched birds were strange, but this summer I found myself watching them, and maybe I'll get a book on the subject. I feel a strong desire for a religious belief that I never thought I'd want, feel close to my ancestors long gone, and echo my father in arguments with my son. I'll still lose….

    One day I bought a house. One day－What a day!－I became a father, and not too long after that I picked up the check for my own father. I thought then it was a milestone for me. One day, when I was a little older, I realized it was one for him too, another milestone．

    If you could have one superpower, what would it be?

    Dreaming about whether you would want to read minds, see through walls, or have superhuman strength may sound silly, but it actually gets to the heart of what really matters in your life.

    Every day in our work, we are inspired by the people we meet doing extraordinary things to improve the world.

    They have a different kind of superpower that all of us possess: the power to make a difference in the lives of others.

    We're not saying that everyone needs to contribute their lives to the poor. Your lives are busy enough doing homework, playing sports, making friends, seeking after your dreams. But we do think that you can live a more powerful life when you devote some of your time and energy to something much larger than yourself. Find an issue you are interested in and learn more. Volunteer or, if you can, contribute a little money to a cause. Whatever you do, don't be a bystander. Get involved. You may have the opportunity to make your biggest difference when you're older. But why not start now?

    Our own experience working together on health, development, and energy the last twenty years has been one of the most rewarding parts of our lives. It has changed who we are and continues to fuel our optimism about how much the lives of the poorest people will improve in the years ahead.

    In Europe, there is no escape for those who do not appreciate art and architecture(建筑). It is a heaven for people who want to feel like they have been transported to famous historical time periods from America. For me, Europe was a complete contrast from America. London and France had a more royal feel than New York, and Rome felt more ancient. I wasn't just on a different continent; it felt like I was in a different century.

    My parents and I visited London, Paris and Rome this summer in celebration of the end of my high school experience. It was supposed to be a break from a life as busy as a bee in New York, the constant stress, the crowded subway rides, and the weary body that had accompanied me for the last four years. It was an opportunity to appreciate Europe the way I couldn't do it just by reading history books.

    My favorite parts of London were the Tower of London and the Churchill War Rooms. As a site of past executions(刑场), the Tower of London displayed punishing devices from the 16^th and 17^th century and told stories of various members of the royal family who had ever been imprisoned in the tower, some even imprisoned by their own family members when they were seen as a threat to the crown. Besides that, I also got to see the royal family's crown jewels, amazingly beautiful.

    The Churchchill War Rooms, though very different from the Tower of London, were also spellbinding from a historic perspective. I am not a history fan, but I enjoy museums, and I took fancy in the Churchchill Museum inside the War Rooms that detailed the events of Churchchill's life and World War II. Everything I saw in it built up his life from his childhood to his last years, creating a three-dimensional Churchchill in my mind who was a person just like myself. He longed for more, he made mistakes, he experienced loneliness and sadness. But he had also done some remarkable things like uniting Britain during World War II.

    Our rewarding trip ended in Rome a couple of days later.