Sergio Peralta was a 15-year-old boy.今年他开始去上一所新学校。He was feeling afraid like most new students. But he also had a secret. He had a hand that was not fully formed （形成）. In the beginning. he wanted to hide （藏） his hand because he didn't want anyone to see it.
One of Peralta's teachers, Jeff Wilkins, found out about his hand. 他想帮助这名新生。He asked his engineering （工程） class to make a new hand for Peralta. The students were excited to help.They spent four weeks making a new robot hand for Peralta by using 3D printer （打印机）.
When they showed the robot hand to Peralta. he was surprised.Now he could catch a baseball with his new hand.
Peralta was thankful that his classmates helped him."I never thought I could do this, he said, "They made a big difference in my life."
Mr. Wilkins was proud of his students. The class showed that engineering was about coming up with new ideas and making life better.
