Rob Stein

That word "microbiome" — describing the collection of bacteria that live in and on our bodies — keeps popping up. This time, researchers say that children whose parents clean their pacifiers by sucking them might be less likely to develop allergic conditions because of how their parents' saliva changes their microbiomes.

Scientists have discovered what may be an important new risk factor for heart disease. And here's the surprising twist: The troublesome substance seems to be a waste product left behind by bacteria in our guts as they help us digest lecithin — a substance plentiful in red meat, eggs, liver and certain other foods.

Doctors say the research further illustrates the complicated relationship we have with the microbes living inside us, and could lead to new ways to prevent heart attacks and strokes.

Scientists reported Wednesday that they had developed a way to measure how much pain people are experiencing by scanning their brains.

The researchers hope the technique will help doctors treat pain better, but the work is also raising concerns about whether the technique might interfere with doctors simply listening to their patients.

Now, when someone is in pain, a doctor has no way to judge its severity except to ask questions, a method that often is inadequate.

Scientists say they have found a way to get a glimpse of people's dreams.

"Our results show that we can predict what a person's seeing during dreams," says Yukiyasu Kamitani, a researcher at the ATR Computational Neuroscience Laboratories in Kyoto, Japan.

Philosophers, poets and psychologists have long shared a fascination with dreams. But Jack Gallant, a neuroscientist at the University of California, Berkeley says solving the mystery of our dreams is one tough problem.

More than 1 million people are dying prematurely every year from air pollution in China, according to a new analysis.

"This is the highest toll in the world and it really reflects the very high levels of air pollution that exist in China today," says Robert O'Keefe of the Health Effects Institute in Boston, who presented the findings in Beijing this week.