There's a variety of reasons why scientists might choose to dedicate a few weeks, a summer, or even a couple of years to volunteering in a developing country. They might wish to learn new skills, for example, or to experience a different culture. But the motivation that almost always tops volunteers’ lists is a desire to apply their time, experience, enthusiasm, and knowledge to making the world a better place.
Say you've decided you'd like to have such an experience. How do you make it happen? The most common way is to go with an international nonprofit that will place you in a host institution, offer you task- and country-specific training, and help you with the logistics of your stay.
It is necessary, of course, to make it work financially, and financial arrangements vary widely. Many nonprofits ask their volunteers to pay a fee of up to several thousand dollars to cover administrative, transportation, housing, and training costs. In some cases, housing is provided free, and volunteers receive a small living stipend. A few volunteers may even earn a local salary. "Volunteers ... contribute their time at no financial gain," says Susannah Taw, spokeswoman of Voluntary Service Overseas (VSO ), which specializes in matching volunteers with a particular need. Almost always, volunteers are encouraged to raise funds to help cover the costs of their stay or the program they will be joining.
Whatever the motivation, or the logistics of the stay, few volunteering experiences ever leave their participants unchanged. Many volunteers find they look at the world completely differently than they did before their volunteering experience. Often, career paths change as well.
In these articles, Science Careers talks to two scientists about what made them decide to volunteer for an international nonprofit, what the experience was like, and how it impacted their personal and professional lives.
Mariel Finucane  always had a strong interest in good works, even before she realized she was also drawn toward the least worldly of scientific subjects: mathematics. For a while, she felt pulled in two directions -- but then she found, in biostatistics and public health, a way to bridge the gap.
Alan Wood  tried to volunteer early in his career, but he didn't make the cut: not enough experience, they said. So he established a successful career in information technology. Then, a decade after his first volunteering attempt, two successful overseas stints -- one in Nigeria and another in Guyana -- transformed his career and his life.
• Previous travel to developing countries is a definite advantage, but it isn't essential.
• Enthusiasm is important, but it's not enough. Make sure you choose a nonprofit that is geared toward the benefit of the local community and be sure your host institution has a clear plan about what you can do to have a positive impact.
• Do your homework before you head out. Read about the country, its culture, and its living conditions. Talk to people who have been there.
• Choose opportunities that look good on your curriculum vitae; otherwise you may find yourself with a giant hole that's difficult to explain to employers, especially if you plan to stay in academia.
• If you are in midcareer and work in a place where such arrangements are feasible, talk to your employer about volunteering abroad. In academia, a sabbatical is an obvious time for an overseas volunteer experience.
• Expect challenges. To meet them, you'll need to be deeply interested, eager to learn, and open-minded.
The Volunteer Guide 
Elisabeth Pain is contributing editor for Europe.