Stephanie revealed the lengths idol stars go to in order to achieve the perfect facial expression on the August 17th episode of Mnet's 'Idol School'.

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Whether it's a cute eye smile or mischievous smirk, most idol group members have their go-to facial expressions that fans go crazy for. On the show, Stephanie told her students the talent didn't come naturally, saying, "The facial expressions of girl groups don't come easily."

She added, "Raina's personality is not normally the way it is on stage, so she practiced her expression for 5 hours. Hong Jin Young also practiced her wink for 8 hours. If a facial expression isn't easy for you, you have to practice it."