Few people enjoyed getting shots at the doctor’s office. But many of these shots are important vaccines (疫苗) that help prevent us from getting certain diseases or types of infection.

Vaccines got their start in Europe in the 1720s, when a British woman named Lady Mary Wortley Montagu was visiting Turkey. She saw Turkish doctors purposefully inoculating (接种) people with small amounts of smallpox. Smallpox is a painful, deadly disease that had no cure at the time. But Lady Montagu was amazed that the patients not only recovered, but then proved to be immune (免疫的) to the disease!

Lady Montagu quickly returned to England, excited to share this new procedure. But inoculation took many years to catch on. One problem was that no one had a correct way of inoculating people safely. Occasionally, patients would become fully infected and then begin spreading the disease. However, inoculation eventually saved enough people for it to become the common practice for preventing smallpox.

Some years later, a scientist named Edward Jenner discovered that people who had been infected with a disease called cowpox became resistant to smallpox. Cowpox was less much harmful than smallpox. Jenner convinced doctors to inoculate people with cowpox, which led to a very safe vaccine and far fewer outbreaks of smallpox. Finally, a French scientist named Louis Pasteur realized that Jenner’s idea could be used to treat other diseases. Since then, vaccines have been made for many other diseases, such as polio, tetanus, and rabies.

Today, scientists and doctors continue to create new vaccines that could potentially save millions of lives worldwide.

Everyone is afraid of something. Maybe you’re afraid of spiders, or heights, or dogs, or the dark. And traditionally, we’ve thought that’s because you learned to be afraid. Probably because you had a bad experience with something at some point. But there’s a different idea out there that’s been getting more attention lately: the idea that fears aren’t just learned. they also can be inherited(遗传).

It sounds like a wild idea. But over the last fifty years, researchers have been studying just how much fears have to do with inheritance and genetics. And their results have been kind of surprising.

In this work, they’ve put a lot of effort into understanding one extreme kind of fear, called a phobia. To get a sense of how much genes influence fear, scientists have begun looking at identical twins. As identical twins have almost the same DNA, researchers can figure out how heritable (遗传的) a fear is by comparing how often specific phobias appear in identical twins as opposed to other brothers or sisters. Because even though twins often have lots of similar experiences, they probably don’t share the types of experiences that cause phobias — like getting bitten by a dog or falling out of a tree.

In 1998, a study of 659 pairs of identical and fraternal twins (双胞)in Australia looked at how many had a fear of blood. The study found that genetics accounted for 71 percent of the variation among those people, meaning genetic factors play a pretty big role in determining whether a person has some specific fear.

A 2016 study also found that fear of dental work was over 30 percent heritable. So, if you are afraid of going to the dentist, it really might not be your dentist’s fault. Overall, first — degree relatives of people with phobias are more likely to have similar phobias than people with no family history.

So, it’s pretty clear that phobias are heritable!

Researchers have discovered the first Earth-sized planet. It was first marked by scientists' using NASA's Kepler telescope(望远镜), so it's called Kepler﹣186f. It lies about 500 light years from Earth and goes around its star.The planet is the right distance from its star for water: not too close or not too far. Water is one important condition that scientists guess is necessary for life. So it could have water and possible life. It's called a true Earth cousin.

"This planet is an Earth cousin, not an Earth twin," said Barclay, who is among a team of scientists reporting on the discovery in the magazine Science this week.

"It's very exciting to find a planet similar to the Earth，"Barclay said. "It's not easy work because things change as we get more measurements."

Scientists don't know anything about the air of Kepler﹣186f, but it will be a task for future telescopes which can study for chemicals that have something to do with life.

"It's possible for life to live in this planet, but that doesn't mean there is life in it," Barclay said.

So far, scientists have found nearly 1,800 planets in the universe.

"The past year has seen a lot of progress in the search for Earthlike planets. Kepler﹣186f is very important because it is the first planet that is the same temperature and is almost the same size as Earth,"scientist David Charbonneau wrote in an email.