Heroin sold in the U.S., like this dose confiscated in Alabama last fall, is often cut with other drugs. Tamika Moore/AL.com/Landov hide caption

itoggle caption Tamika Moore/AL.com/Landov

Michael Arnott, of Cambridge, Mass., says he used to have trouble staying awake on long drives. Sleep specialists discovered he has obstructive sleep apnea, though not for the most common reasons — he isn't overweight, and doesn't smoke or take sedatives. M. Scott Brauer for NPR hide caption

itoggle caption M. Scott Brauer for NPR

Frozen sperm straws and embryos are stored in liquid nitrogen, in a process known as cryopreservation. One question confronting the courts: Should embryos such as these be treated as property, or as children subject to custody action? Veronique Burger/Science Source hide caption

itoggle caption Veronique Burger/Science Source
Katherine Streeter for NPR

Bacillus subtilis may look like pasta under the microscope, but the bacteria are common in the gut of humans. Could the microbes be contributing to our belly fat? Too soon to tell, scientists say. BSIP/UIG via Getty Images hide caption

itoggle caption BSIP/UIG via Getty Images

A daily pill called Addyi is the first medicine to be approved for the purpose of boosting women's sexual desire. Allen G. Breed/AP hide caption

itoggle caption Allen G. Breed/AP

"I was more so afraid of the stigma attached to the disease than the actual disease," says Guy Anthony. Courtesy Guy Anthony hide caption

itoggle caption Courtesy Guy Anthony

Cris and Valerie Fiore hold one of their favorite pictures of their sons Anthony (with the dark hair) and Nick. Anthony died from a heroin overdose in May 2014 at the age of 24. Cris Fiore's eulogy described his son's death as a shock, but "not a surprise." Anthony had been addicted to heroin for years. Ben Allen/WITF hide caption

itoggle caption Ben Allen/WITF

This genetically modified yeast can convert sugar into powerful opioid drugs. Scientists working with the modified yeast strains are required to register them with the Drug Enforcement Administration and keep the yeast under lock and key. Courtesy of Christina Smolke/Stanford University hide caption

itoggle caption Courtesy of Christina Smolke/Stanford University

We all get by better with a little help from our tunes. iStockphoto hide caption

itoggle caption iStockphoto

Republican presidential candidates (from left) Donald Trump, Jeb Bush, Mike Huckabee, Ted Cruz and Rand Paul during the Republican presidential debate in Cleveland on Aug.6. Andrew Harnik/AP hide caption

itoggle caption Andrew Harnik/AP

A Texas lawsuit filed against 30 insurance plans in 15 states alleges that the companies overcharged Medicare for doctors' house calls. Laughing Stock/Corbis hide caption

itoggle caption Laughing Stock/Corbis