The Nation's Little Sister glows in the dark IU as she showed off her matured beauty on Instagram on Saturday.

In the picture, IU poses by the balcony of a building with the city skyline as her backdrop. She is smiling at the camera as she's leaning against the railing. Her skinny body and the ant waist especially caught much attention.

IU will be performing at the '2015 Melody Forest Camp' being held on September 19 and 20.