Singing "Let It Go" may seem so 2013 (and '14, for that matter), but it's about to come back in the most heartwarming way.

A team of nurses at New Royal Hospital for Sick Children in Glasgow, Scotland performed the already classic song with a 3-year-old patient named Millie McColl who's battling cancer and shared it on the girl's Facebook page.

Millie is fighting stage 4 neuroblastoma, so the nurses took mic in hand and showed off their fierce dance moves in an attempt to cheer up Millie.

Around the 1:50 mark, Millie herself grabs the microphone to help sing. It's truly a moment that will get you misty-eyed.

You can donate to help Millie's family pay for treatment.