Not forgetting the special occasion, f(x)'s Amber took to her Instagram to leave a sweet message, along with a selca of the 4 f(x) members. She wrote, "Love and miss these girls. Thank MeU for always being amazing! Always know the girls and I are always doing our best for you guys and we always know you guys are doing the same. Never give up! Love ya!"

Meanwhile, Amber is currently busy preparing for her U.S. debut. Happy 9th anniversary, f(x)!