The 2010 TIME 100

It's fine to help the developing world, but first you have to know what it needs. Amy Smith does.

An engineer and the founder of MIT's innovative D-Lab, Smith, 47, is a former Peace Corps volunteer who spent parts of her childhood in India and Botswana. She's the creator of a hammer mill that converts grain to flour and an incubator that does not require electricity. Her design philosophy is elegant: create simple machines that meet particular needs and then build them locally.

Smith is also a teacher, taking kids to Haiti and Africa, where they design pumps, bicycle parts and other gear people need. Her machines are one of her gifts to the world; the students she trains will be an even more enduring one.

Pentland is a professor in the MIT Media Lab and the director of its entrepreneurship program

TIME 100 Social-Networking Index: 0