Former first lady Michelle ObamaMichelle LeVaughn Robinson ObamaObamas buy home on Martha's Vineyard Michelle Obama to donate 0K to Girls Opportunity Alliance Fund Julia Roberts, Michelle Obama traveling to Southeast Asia for Girls Opportunity Alliance MORE on Tuesday revealed one phrase that was on her mind on the day of President TrumpDonald John TrumpPence: It's not a "foregone conclusion" that lawmakers impeach Trump FBI identifies Pensacola shooter as Saudi Royal Saudi Air Force second lieutenant Trump calls Warren 'Pocahontas,' knocks wealth tax MORE's inaugural, also the day she and former President Obama left the White House.

"Bye, Felicia," Obama said Tuesday on "The Tonight Show Starring Jimmy Fillon" as Fallon held a photo showing Obama and her husband boarding a plane following the inauguration.

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“A lot was going on that day. That was a day," the former first lady added.

Obama told Fallon that she is optimistic about the future of the country because of the young people and says older generations owe the younger ones that "hope" and "optimism."

"Everywhere I go, I get to see young people. And we owe young people that optimism, that hope, because what’s the alternative? And they come into this world ... with so much promise," she said.

Obama is currently on tour promoting her new memoir, "Becoming."

The book quickly became the best-selling book of 2018 following its release last month and has already sold more than 3 million copies.