I was nervous coming here today,” said Jennifer Lopez, as she turned the corner onto a residential street in the Bronx. It was a cool afternoon in late spring, and Lopez was wearing a loose bright pink jogging suit and sequined platform sneakers. She is a kind of physical wonder: small but strong, narrow everywhere except for her famous perfectly round derriere. “This is the house I grew up in,” she said, stopping in front of a white two-story surrounded by an ornate metal gate. It was set apart from the rest of the houses on the block by an alley in the back and a vacant lot next door. Across the street, in a kind of homage to Lopez, there was a banner for the Rising Stars School. “I didn’t go to that school,” Lopez said, still staring at her former home, where she lived with her parents and two sisters. She pointed at a back window that faced the empty lot. “I would look out that window to see if my boyfriend was coming, and then I’d run out the door,” she said, laughing. “I’m the middle sister. All three of us girls shared a room. I was into sports and dancing. I ran track. I have a lot of stamina.” Lopez laughed again. “I was built for the long run.”