Cycling has at least tripled over the past two decades in several big cities across the U.S., including Minneapolis, Chicago and San Francisco. Jonathan Steinberg hide caption

itoggle caption Jonathan Steinberg

Monica Hanson (top left) is the eldest of four daughters and says she fell into the role of firstborn naturally. Her sisters (from left to right) are Elena Lynn, Maria Godoy (a senior editor at NPR.org) and Olga Czekalski. Also pictured (bottom left) is her daughter, Erica, and Erica's cousins Kelsey and Taylor Lynn. Courtesy of Monica Hanson hide caption

itoggle caption Courtesy of Monica Hanson

Researchers from Yale University found that kids are seeing more fast food ads than ever before. Jonathan Barnes/iStockphoto.com hide caption

itoggle caption Jonathan Barnes/iStockphoto.com

A jogger passes two women napping on the National Mall near the U.S. Capitol. Regular exercise may reduce the chance of getting a cold. Cliff Owen/AP hide caption

itoggle caption Cliff Owen/AP

Researchers are looking at ways to get kids to pick healthier foods in their school cafeterias. One middle school found that when they put chocolate milk 6 inches behind white milk, many kids suddenly opted for the white milk instead. The school pictured wasn't involved in the study. Toby Talbot/AP hide caption

itoggle caption Toby Talbot/AP

Peter Sherry demonstrates a hamstring stretch. Maggie Starbard/NPR hide caption

itoggle caption Maggie Starbard/NPR

Bee colonies across the country are dying because of colony collapse disorder, and researchers say a combination of a virus and a fungus could be playing a key role in the bees' sickness. Christopher Tompkins/iStockphoto.com hide caption

itoggle caption Christopher Tompkins/iStockphoto.com

Carrot farmers are banking on a $25 million ad campaign to make carrots as cool as junk food. Crispin Porter + Bogusky via AP hide caption

itoggle caption Crispin Porter + Bogusky via AP

Rachel Bateman, 9, has braces to correct an overbite. Her orthodontist opted not to use expanders to expand her upper arch. Mike Ruocco/NPR hide caption

itoggle caption Mike Ruocco/NPR

This computer illustration shows a kidney stone in the renal pelvis. Although a major component of kidney stones is calcum, a new study shows that a calcium-rich diet may help inhibit their development. 3D Clinic/Getty Images hide caption

itoggle caption 3D Clinic/Getty Images