Every time your fingers touch your cell phone, they leave behind traces of chemicals. And each chemical offers clues to you and your activities. By analyzing them. scientists might be able to piece together a story about your recent life, a new study finds.

A molecule is a group of atoms. It represents the smallest amount of some chemical. Your skin is covered in molecules picked up by everything you’ve touched. With each new thing your skin contacts, you leave behind some small share of what it’d touched earlier.

Researchers at the University of California. San Diego (UCSD)recently analyzed such chemical leftovers on the phones of 39 volunteers. The study was led by biochemist Amina Bouslimani. To explore those remains, the UCSD team wiped the surface of each volunteer’s phone with a cotton swab(药棉签). The scientists also swabbed each person’s right hand.

Then the researchers compared the chemicals found on each cell phone. The scientists discovered as many of the molecules as they could. They then compared these to a database of chemicals. Pieter Dorrestein. a UCSD pharmaceutical chemist, had helped set up that database a few years earlier, which contains various substances, including spices, caffeine and medicines.

Traces of anywhere from hundreds to thousands of different molecules turned up on each phone. The molecules reflected what had been in the body, and what each person had handled before touching the phone. From all these molecules, Bouslimani says. “We could tell if a person is likely female, uses high-end cosmetics, dyes her hair, drinks coffee, prefers beer over wine or likes spicy food.”

Police already use molecular analyses to look for traces of explosives or illegal drugs. To date, Dorrestein says. he’s never heard of police using phone remains to narrow down behavioral clues to search for a suspect. But detectives might one day use such data to track down someone who left a phone behind at a crime scene.

Imagine a drug that could enhance a child’s creativity and critical thinking. Imagine that this drug was simple to make, safe to take, and could be had for free. The nation’s leading pediatricians (儿科医生) say this miracle compound exists. In a new clinical report, they are urging doctors to prescribe it liberally to the children in their care.

“This may seem old-fashioned, but there are skills to be learned when kids aren’t told what to do,” said Dr. Michael, a Harvard Medical School pediatrician who led the drafting of the call. Whether it is rough physical play, outdoor play or pretend play, kids obtain important lessons to make things up as they go. Actually, play fosters children’s creativity, cooperation, and problem-solving skills, all of which are critical for a 21-century workforce. When parents engage in play with their children, it builds a wall against the harmful effects of all kinds of stress. The pediatricians’ appeal comes as kids are being squeezed by increasing academic demands and the constant invasion of digital media.

The trends have been a long time coming. Between 1981 and 1997, studies showed that the time children spent at play declined by 25 percent. Since the adoption of sweeping education reforms in 2001, public schools have steadily increased the amount of time devoted to preparing for standardized tests. Even kindergartens are not excluded. By 2009, a study of Los Angeles kindergartens found that five-year-old kids were so burdened with academic requirements that they were down to an average of just 19 minutes per day for free play. Plus, kids’ growing time spent in front of screens and digital devices, even among preschoolers, is another playtime thief.

Play may not be a hard sell to kids. But UCLA pediatrician Carlos Lerner acknowledged that the pediatricians’ new prescription may meet with skepticism from parents, who are anxious for advice on how to give their kids a leg up in the world. Lerner said, “It’s liberating to be able to offer them this advice: that spending time with your child and letting him play is one of the most valuable things you can do.”