Before they were one of the top K-pop groups in the world, EXO were hard-working trainees.

In a new video shared on Twitter on July 28, SM Entertainment's boy band EXO reveals their feelings about being K-pop trainees at the major agency. The video, a promotion for the upcoming SM Entertainment documentary "SMTOWN The Stage," features never before seen footage of EXO during their trainee period.

The new footage shows EXO preparing to debut and has the members discussing how they felt during their pre-debut life.

"I was a trainee for about six years," EXO's leader Suho revealed. "I will never forget those times."

The nine members of EXO discussed the hardships, and how they felt during their pre-debut times.

"When I first joined the team, I was very bad at dancing and moving my body," said vocalist D.O. "Even so, I practiced a lot in order to catch up with the rest. That period of time is unforgettable to me."

After each member reminisced, Kai spoke about how EXO feels now that they've achieved success.

"At this moment, I think that we really need to reflect," he said. "We shall became an EXO that doesn't forget our initial resolution.

The video ends with Kai asking fans for much love.

"SMTOWN The Stage" will be released on August 13 in theaters in South Korea.

EXO, 연습생 시절 미공개 영상 에서 최초 공개! #EXO #엑소 #smtown_the_stage #8월13일_대개봉 https://t.co/0gMMk3zQQy

— SMTOWN THE STAGE (@smtown_thestage) July 28, 2015

-