The 82 schoolgirls released by Boko Haram Islamist militants have met Nigerian President Muhammadu Buhari.
They were escorted to the reception in the capital Abuja by armed soldiers, after a check-up at a medical centre.
Mr Buhari said he was joyous that they were free. He is now travelling to London for medical reasons as concern grows for his health.
A spokesman said there was "no cause for worry" and that he was travelling for a "follow-up" consultation.
Mr Buhari, 74, returned from the UK in March after seven weeks of sick leave. When he returned home he said he had never been so ill in his life.
What illness he has remains undisclosed but concerns about his condition grew in recent weeks after he missed several cabinet meetings.
The girls were handed over on Saturday in exchange for Boko Haram suspects after negotiations.
They were from a group of 276 abducted in north-eastern Nigeria in 2014. Before the latest release, about 195 of the girls were still missing.
The number of Boko Haram suspects released by authorities remains unknown.
"I cannot express in a few words how happy I am to welcome our dear girls back to freedom," Mr Buhari told the girls in Abuja, according to his office.
"On behalf of all Nigerians, I will like to share my joy with you," he said.
Mr Buhari would have left earlier on Sunday to London but wanted to receive the schoolgirls, his spokesman Femi Adesina said.
Arriving in Abuja earlier, some of the girls looked tired and confused by all the attention after spending three years in captivity.
Before being taken to the capital, they were brought by road convoy from a remote area to a military base in Banki near the border with Cameroon.
Our reporter says that many families in Chibok will be rejoicing at this latest news, but more than 100 of the girls taken have yet to be returned.
"This is good news to us. We have been waiting for this day," Christian pastor Enoch Mark, whose two daughters were among those kidnapped, told Agence France-Presse.
"We hope the remaining girls will soon be released." It was unclear whether his daughters had been freed.
A statement from a spokesman for President Buhari earlier said he was deeply grateful to "security agencies, the military, the Government of Switzerland, the International Committee of the Red Cross, and local and international NGOs" for playing a role in the operation.
In a later BBC interview, presidential spokesman Garba Shehu added: "With all of these things together we negotiated over a period of several months, and at the end of it some of their [Boko Haram's] members were exchanged for the 82 girls."
After the Government Girls Secondary School in Chibok, Borno state, was raided in April 2014, more than 50 girls quickly escaped and Boko Haram then freed another 21 last October, after negotiations with the Red Cross.
The campaign for the return of the girls drew the support of then US First Lady Michelle Obama and many Hollywood stars.
Last month, President Buhari said the government remained "in constant touch through negotiations, through local intelligence to secure the release of the remaining girls and other abducted persons unharmed".
Many of the Chibok girls were Christian, but were encouraged to convert to Islam and to marry their kidnappers during their time in captivity.
Boko Haram has kidnapped thousands of other people during its eight-year insurgency aimed at creating an Islamic caliphate in north-eastern Nigeria.
More than 30,000 others have been killed, the government says, and hundreds of thousands have been forced to flee from their homes.
Ok, who is watching the clock? Those seconds aren't going to count themselves. The only way to understand time is to be its witness. Although that can get depressing. Let's focus on the light and cool.
History...
Calculate Figure It Out GIF by OriginalsGiphy"If you are an 80-year-old American, you have lived through approximately 1/3 of our nation's entire history."
Those Days...
"The 80s were 40 years ago."
"This is what messes me up because I was born in 82 and graduated high school in 2000 so for some reason my brain is stuck on the 80's being twenty years ago. The 70's thirty years ago etc etc. I have to stop and realize sometimes that my concept of how long ago things happened is way off."
Time goes by...
"We observe that light travels at 186,000 miles a second, but given the vast size of the observable universe, that's a snail's pace. But from the point of view of a particle of light, time doesn't even exist."
"Time slows down as you approach the speed of light, and theoretically stops completely when you reach the speed of light."
Years Gone By...
"MLK Jr. and Anne Frank were born in the same year."
"Betty White was born in 1922. Automatically pre-sliced packaged bread loaves became commercially available in 1928. Betty White is six years older than sliced bread."
Long Live the Queen!
queen elizabeth images GIFGiphy"The queen and Marilyn Monroe would've been the same age."
"And Marilyn Monroe and Andy Griffith were born on the same day!"
- osme1
I swear Liz is going to outlive dirt. Wait, I believe she already has. Well she won't be alone, she'll have Betty White. At least she better have Betty. Time is nothing without Queen Betty.
TV Time
Season 2 Omg GIF by Paramount+Giphy"Happy Days was a TV show made in the 1970s-80s about teenagers in the 1950s. Similarly, That 70s Show was made in the 90s-00s about teenagers in the 70s. If a similar show were to be made today, it would be about teenagers in the 2000s."
- VVillyD
A Croc
"If a T-Rex imagined a creature as ancient as the T-Rex is to us, it would be a Stegosaurus. If that Stegosaurus imagined a creature as ancient as the Stegosaurus is to us, it would be a Crocodile. If that Crocodile imagined a creature as ancient as that Crocodile is to us, it would be a Shark."
On the Clock
"On a twenty four hour clock the amount of time that humans have been on the earth would total around five seconds."
"How about this one: If Homo Habilus first appeared at midnight, 24 hours ago, that means the first Homo Sapiens appeared at 9:25 PM, or about 2 and a half hours ago. The first human civilization, in lower Mesopotamia, appeared at 11:57 PM, or about 3 minutes ago."
"The Western Roman Empire fell at 11:59 PM, or 1 minute ago. Everything that has happened since - the Crusades, the Plague, the discovery of the New World, the world wars, all of it - has happened in the last minute of human existence."
And that's just OUR Sun...
"The span of our lives are so insignificantly small that our Sun will last another 5 billion years. That's 9 zeros people. Our eldest live to around 100 in the best places. That's 50,000,000 (50 million) times longer than any person can reasonably expect to live. And that's just OUR Sun. The universe as a whole has probably existed for magnitudes longer than that already and will continue to exist until the end of time as we know it."
Tell Me a Story
william shakespeare GIF by will herringGiphy"We know what a good storyteller Shakespeare was but there were Greek playwrights who wrote shows nearly 2,000 years earlier that are pretty good, too."
I hate time. Only because I'm petty and irritated of the amount I squandered. That's neither here nor there though. Time marches on and continues to amaze. I'll keep watching.
Want to "know" more? Never miss another big, odd, funny, or heartbreaking moment again. Sign up for the Knowable newsletter here.