CARL AZUZ, CNN ANCHOR: Thank you for taking 10 minutes to get up to speed on world events. This is CNN 10, where we provide down the middle explanations of what's going on. I'm Carl Azuz. It's great to see you.

Venezuela has been in the news a lot this year. Massive protests have been taking place since cities across the country, including Caracas, the Venezuelan capital. Since April, more than 120 people have died in protests against the government. Why?

The Venezuelan economy has practically collapsed. Its government gets almost half of its revenue from oil. It nationalized or took over Venezuela's oil industries in 1976.

But when oil prices dropped in recent years, so did Venezuela's revenue and that led to extreme inflation, a recession that's lasted for years, an unemployment rate of 25 percent. Venezuelan President Nicolas Maduro blames his political opponent and the United States for his country's economic problems.

A vote last month allowed President Maduro to replace his country's legislative branch. It used to be controlled by a political party that opposed him. The new one is filled with people who support him.

The president says the constituent assembly will help bring peace to a divided Venezuela. But his opponents, as well as other countries like the U.S. called the vote a sham, and America put economic penalties on President Maduro. He faces growing crises at home and abroad.

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PAULA NEWTON, CNN INTERNATIONAL CORRESPONDENT: Venezuelan politics have always been complicated and temperamental. But even more so now, as the crumbling economy has plunged this country into a very dangerous political stalemate.

In 1999, Hugo Chavez was elected president and he turned to his very specific and personal brand of socialism, Chavismo. He gave out free flats, television sets, refrigerators, fixed prices for basic things, like flour and eggs.

And that made many people in Venezuela happy. It totally brought up the standard of living in the middle class. The problem was there was no way to pay for these things.

When Hugo Chavez died in 2013, his handpicked successor, Nicolas Maduro, was elected president. He continued with Chavismo. The problem was that the price of oil collapsed from $100 a barrel to less than $50. The economy has never recovered. One in four Venezuelans is unemployed. Inflation could hit 700 percent this year and there are shortages of very basic things like that flour, that medicine, even things like toilet paper.

In the meantime, President Nicolas Maduro was being encouraged by the international community to sit down with the opposition and negotiate an opposition that he continues to try and undermine. The opposition here won elections in 2015 for the national assembly, an assembly that Nicolas Maduro continues to undermine.

As of now, the international community would like Nicolas Maduro to release hundreds of political prisoners, trying to stabilize his economy and come to some kind of peace with the opposition.

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AZUZ (voice-over): Ten-second trivia:

Which of these ailments is not currently treatable by a vaccine?

Opioid addiction, chickenpox, diphtheria or yellow fever?

Though scientists are working on one, experts say they're years away from actually producing the vaccine that helps with opioid addiction.

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DONALD TRUMP, PRESIDENT OF THE UNITED STATES: The opioid crisis is an emergency and I'm saying officially, right now, it is an emergency. It's a national emergency. We're going to spend a lot of time, a lot of effort, and a lot of money on the opioid crisis.

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AZUZ: All right. A couple of things about this. One, declaring a national emergency, which you just heard U.S. President Donald Trump do, allows a leader to use special powers to take on a crisis. More resources, including money, are made available to government and state agencies, to go after the problem.

Two, the American opioid crisis is significant. It's been growing for years. The U.S. Centers for Disease Control says that since 1999, the number of American overdosed deaths involving opioids, these are manmade painkillers, has quadrupled.

The U.S. government has been taking action for several years to address the epidemic, but new data suggests that its efforts aren't working, with opioid related deaths having increased over most of last year. A bipartisan commission, a group including Republicans and Democrats, recommended that President Trump make the emergency declaration.

Turning our attention skyward. Though we don't know how often someone can experience a total eclipse of the heart, scientists say a total solar eclipse when the moon passes between the earth and the sun is visible from somewhere on our planet every year and a half or so. It's been 38 years since one shadowed the U.S. though, and 99 years since a total solar eclipse crossed the entire country. So, we and our friends at CNN.com/eclipse are covering the moon as it covers the sun.

In ancient China, some people who saw these events believe a dragon was eating the sun. In countries across the Mediterranean, people thought it was a sign that the king would die. Though the phenomenon is viewed with a lot more excitement than fear today, it still needs to be viewed carefully.

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JENNIFER GRAY, CNN METEOROLOGIST: A total solar eclipse is a rare and spectacular event. But if you plan on watching the show, you do need to take some precautions to protect your eyes. Never look at the sun with naked yes, and never, ever look at it through binoculars or a telescope unless equipped with a solar filter.

You can purchase inexpensive, specialized glasses that are designed for looking at the sun. They should meet the international standard for light blocked by a filter. And remember, though solar filters block most harmful radiation, you still need to take frequent breaks from looking directly at the sun.

If you're in a position to see totality, watch until the last bright spot on the edge of the moon disappears with your safety gear on, and then you can take it off. While the moon completely covers the sun, it is safe to view directly with naked eyes, but take care to put your safety gear back on as soon as any of the sun reemerges.

Another way to safely view the eclipse is to use a pinhole viewer. To make one, you just need two pieces of cardboard or paper. Punch a hole in one and use it to project an image on the other piece of paper. When the light dot turns black, you know it's safe to look up at the sun.

A total eclipse will leave a permanent mark on your memory, but protect your eyes to make sure it doesn't leave a permanent mark on your retina.

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AZUZ: Or maybe we should call this two out of two, because it's about twins y'all. According to BabyCenter.com, out of every 100 births in America, three bring twins into the world. And in a town in Ohio that was founded by twins, an event honoring identical and fraternal twins just celebrated its twin centennial, its 200th year of honoring twins.

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UNIDENTIFIED MALE: We're twins and are married to twins. But just like everybody else looking at us, there are days that I cannot tell them apart.

SUBTITLE: Seeing double for science.

UNIDENTIFIED MALE: This is Twins Days Festivals. It's here in Twinsburg, Ohio, for twins. It's a place we outnumber the singletons, and the people who are not twins are the ones who feel out of place.

SUBTITLE: The Malm twins met, proposed and married at the festival.

UNIDENTIFIED FEMALE: We met them in '91, and got engaged in '92 and we got married here in '93.

SUBTITLE: They've been coming for decades.

UNIDENTIFIED MALE: The twins like us have been here for 25 years.

SUBTITLE: They are among thousands of twins who take part in scientific studies at the festival.

UNIDENTIFIED MALE: We also have the festival here. They set up science studies from universities all around the United States. In fact, the FBI has been using the twins for years now to develop their facial recognition.

SHANNON WEITZ, SCIENTIST, CLAY: So, twin studies can really tell us how the environment, your lifestyle, your habits can influence your every day life. So, in our case, we're interested in aging skin and how young you look or how healthy your skin might look.

DANIELLE REED, BEHAVIORAL GENETICIST, MONELL CHEMICAL SENSES CENTER: We're asking the question, just like some people are color blind, our question is whether some people are taste blind and if so, to what?

UNIDENTIFIED MALE: By having twins that's genetically the same or really close doing the research, it's far easier because they can weigh what nature has done versus nurture.

CLARENCE YORK, ASSISTANT PROFESSOR OF MASS COMMUNICATION, KENT STATE UNIVERSITY: How genetics influence our frequency of news use and our news behaviors.

NICOLE OSBORN, FORENSIC SPECIALIST, LOS ANGELES POLICE DEPARTMENT FEMALE: Finger prints are still unique across individuals regardless if they're twins or not. But identical twins have more in common than say just regular siblings.

UNIDENTIFIED MALE: I didn't realize how important twins were in research until I started coming to the festival.

UNIDENTIFIED FEMALE: It looks like a party, but it's really science.

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AZUZ: Science, someone say, is twice as useful, might give non-twins a twinge of jealousy, might lead to discoveries that are simply twingenius. And whether the findings in Twinsburg are identwincal with other research, there's no question it's twins for the twin (ph).

I'm Carl Azuz and CNN twin will be back tomorrow. I hope you will two.