This 30-year-old millennial helped found — and now runs — Facebook. His net worth is estimated at more than $33 billion. Marcio Jose Sanchez/AP hide caption
On Instagram, @ncmpls describes herself as #female #26 #married #adventurer #designer #lover #optimist @ncmpls/Instagram hide caption
Anti-Vietnam War demonstrators hold up signs and raise their hands toward the White House in a protest. The term "baby boomers" stuck for this generation because of their tumultuous youth. AP hide caption
More than 65 percent of first marriages today are between couples already living together. For millennials, cohabitation is almost a rite of passage. Oliver Hoffmann/iStock hide caption
The headquarters of Monsanto, near St. Louis, Mo. Monsanto is the world's largest seed supplier. Juliette Michel /AFP/Getty Images hide caption
Young adults seem to be taking advantage of health coverage. But they're still skipping the flu shot. Image Source/Corbis hide caption
We asked you to send in your embarrassing instant messenger handles from days gone by. Thanks for sharing, Blondsoccerplyr, AgentGiggleChunk and absofsteel3616! iStockphoto hide caption
The phone company Vonage reported a drop in voice mail retrievals over the past year. Many of those ignoring voice mails are millennials. iStockphoto hide caption
Phillip Underwood and Michelle Sheridan and their children, Logan and Lilliana, gather in their living room in Frederick, Md., after a long day of work and school. The couple had delayed marriage, in part for financial reasons. James Clark/NPR hide caption
Millennials are often painted as the entitled, selfie-snapping generation. But many researchers say that "me" time will help young people make better decisions in the long run. © Eugenio Marongiu/iStockphoto hide caption
The Manhattan-based headquarters of Charity: Water. Elise Hu/NPR hide caption
Millennials seem to prioritize the environment, but may want to dissociate from the "treehugger" baggage of the term "environmentalist." Getty Images hide caption
Millennial focus group: Arturo Chang (from left), Shaza Loutfi, Alexa Graziolli, Stephen Crouch, Jessica Ramser. Not pictured: Ginger Gibson. Rachel Lushinsky/NPR hide caption
Rapper Lil Jon appears in a new ad for Rock the Vote's 2014 campaign. The organization was founded to get Generation X engaged in politics, and is adapting its tactics to reach millennials. Courtesy of Rock the Vote hide caption
Fabianie Andre with her 3-year-old daughter, Leilah, at their home in suburban Boston. Andre is one of many millennials who lack a college education. Asma Khalid/WBUR hide caption