Taylor Swift delivered a heartfelt, heartwrenching performance of her original song, 'Ronan,' at the Stand Up 2 Cancer telethon on Friday night (Sept. 7). Warning: You're going to need tissues for this.

Swift wrote 'Ronan' about a three-year-old boy of the same name ater reading a blog post by his mother, Maya Thompson. Thompson is credited as a co-writer of the song. The actual Ronan passed away after battling neuroblastoma in 2011.

Accompanied only by a guitar and a lone drum, Swift sits on a stool and croons softly, "I remember your bare feet down the hallway / I remember your little laugh / Race cars on the kitchen floor / Plastic dinosaurs / I love you to the moon and back. ... Come on baby with me, we're gonna fly away from here / You were my best four years." Swift addressed the death of the tot poignantly and heartbreakingly, singing, "Flowers pile up in the worst way" and describing the painful drive home. While her pitch may not be the best it's ever been in this performance, we're chalking it up to the fact that she was probably struggling not to cry while she sang it. It's simultaneously warm, sentimental and absolutely haunting.

All proceeds of 'Ronan,' which is available on iTunes, will go to fight cancer. Good luck listening to it without crying -- we only lasted about 30 seconds before we started lying and saying our eyes were just really, really watery.