The Olympic cauldron has been lit, marking the end of the opening ceremony and symbolizing the start of the 2020 Tokyo Games.

The Olympic flame made its way to Tokyo during the Olympic torch relay, which began several months ago at Olympia, Greece. Upon entering the stadium, the flame was passed between various people before reaching the cauldron.

At one point, the torch was carried by a physician and a nurse who have treated many COVID-19 patients -- a nod to all the health workers on the front lines of the pandemic.

But it was Japanese tennis player Naomi Osaka who ultimately lit the cauldron. Osaka, 23, was born in Japan to a Japanese mother and Haitian father but was raised in the United States.

It's the first time Osaka has competed at the Olympics. The four-time Grand Slam singles champion has always represented her birth country in competitions -- and now at the Games.

After a musical performance of John Lennon's "Imagine" featuring singers from around the world, some 1,800 drones lit up the skies over the stadium in the formation of a globe.

Seiko Hashimoto, president of the Tokyo 2020 organizing committee, and Thomas Bach, president of the International Olympic Committee, then took the stage for brief remarks.

The pandemic loomed large over both speeches this year. Hashimoto, a seven-time Olympian herself, addressed the crowd in Japanese.

"Today, with the world facing great challenges, some are again questioning the power of sport and the value of the Olympic Games," Hashimoto said.

"Citizens of the world and the people of Japan are with us in spirit as athletes from around the globe gather here at the Olympic stadium under the Olympic flag," she added. "Here is a vision for the future, one that embodies unity in diversity, one of peace and respect for one another."

Hashimoto called this "the power of sport and an expression of the fundamental values of the Olympic movement."

Bach then expressed gratitude to the people of Japan for hosting the events despite many challenges, referencing the nation's reconstruction following the earthquake and tsunami in 2011 and then resilience through the coronavirus crisis.

Bach also emphasized the importance of hope, especially through sports, during difficult times.

"The pandemic forces us apart," Bach said. "But today wherever in the world you may be we are united in sharing this moment together. The Olympic flame makes this light shine brighter for all of us."

Japan's Emperor Naruhito, whose grandfather opened the 1964 Summer Olympics in Tokyo, then officially declared the Games open as a fireworks show illuminated the stadium.

After a dance- and music-filled opening, some of the Olympic athletes from the 205 participating countries marched into the stadium for the hourslong "Parade of Nations" segment of the ceremony.

The parade has been part of the opening ceremonies at the Games since the 1908 Summer Olympics in London. Traditionally, each nation chooses just one flag-bearer for the parade. But this year, countries were actively encouraged to select both a male and female representative to carry their flag.

For the first time in Olympic history, countries entered in alphabetical order according to their names in the Japanese language, using the katakana alphabet.

However, the first team to enter is always Greece because that's where the ancient Games originated in 776 B.C.

This year, the second team to enter was the special team of refugee athletes put together by the International Olympic Committee. The team's name, IOC, is ahead of every other alphabetically in katakana.

Syrian-born swimmer Yusra Mardini and Eritrean-born long-distance runner Tachlowini Gabriyesos were selected to carry the special flag for the Refugee Olympic Team during the lap of the stadium.

With Russia's team name, flag and national anthem banned from the next two Olympics over allegations of a state-backed doping program, the country's athletes marched into the stadium this year with the Olympic flag and under the name ROC, an acronym for Russian Olympic Committee.

It's the second time that Russia has not been able to use its own name, flag or anthem at the Games. During the 2018 Winter Olympics in Pyeongchang, Russia's team was branded as OAR, an acronym for Olympic Athletes from Russia.

Among the athletes marching in for Syria was 12-year-old table tennis player Hend Zaza, the youngest athlete at the Tokyo Olympics.

Zaza was one of the two flag-bearers for Syria's team.

Team USA was third-to-last to enter. Basketball player Sue Bird and baseball player Eddy Alvarez were the flag-bearers.

Bird, a 40-year-old point guard for the Seattle Storm, is the oldest player in the Women's National Basketball Association. Born in New York, Bird holds duel U.S.-Israeli citizenship. She has won four Olympic gold medals.

Alvarez, a 31-year-old infielder for the Miami Marlins, has also been to the Olympics before but not for baseball. Prior to his professional baseball career, Alvarez won a silver medal in the 5,000-meter relay in speed skating with Team USA at the 2014 Winter Olympics in Sochi. Born in Miami to Cuban immigrants, Alvarez became the first Winter Olympics athlete and the first non-baseball Olympian since Jim Thorpe to play Major League Baseball following his MLB debut in August 2020.

The last team to enter is always the host country, which is Japan for these Games. Wrestler Yui Susaki and basketball player Rui Hachimura carried the Japanese flag.

Born in Japan's Toyama prefecture, Hachimura is a 23-year-old forward on the Washington Wizards in the National Basketball Association.

Crowds similar to what is typically seen outside major political summits gathered near the venue as the opening ceremony began. While the crowds aren’t massive, they are vocal.

The chants, police whistles and loudspeakers could even be heard inside the stadium.

The mood inside the nearly empty venue was described as solemn by ABC News reporters in attendance and a bit like a dress rehearsal due to the absence of spectators.

As the athletes marched in, however, they were said to be in good spirits despite not being greeted by live applause.

The Olympics host city of Tokyo is currently under a state of emergency order as new COVID-19 cases have spiked in the lead-up to the Games. Many locals have expressed fears that the games will spark a surge in cases, and polls show a majority of the Japanese public were against hosting the Games this year.

The government and organizers, however, doggedly forged ahead.

On the eve of the opening ceremony, Tokyo health officials reported a nearly six-month high in new COVID-19 cases. Some 1,979 new cases were reported, the highest single-day figure since January.