This video segment adapted from Curious presents the journey of Mark Davis.  In high school, Mark Davis ran the 400 in track.  His goal was to have the best time for this event in the United States.  In college, his aspirations changed.  He decided to study chemical engineering because it was the most challenging major.  After college, he began research at Cal Tech, where he solved problems thought to be unsolvable.  When his wife contracted breast cancer, she posed a new challenge for him.  She asked him to find an effective cancer treatment that would not make patients terribly sick.  With no background in cancer research, he took on the challenge and was successful.