"Ronan" was inspired by Maya Thompson's son.

Monday night was an emotional night for Taylor Swift and those in attendance at her show in Arizona. Taylor slowed things down to perform the song "Ronan" which was inspired by a four-year-old boy who lost his battle with cancer.

His mother Maya Thompson was in the audience.

Taylor spoke of Maya's blog detailing her son's fight. "One of the bravest things a human being can ever do is to go through something absolutely unbearable and then share their experience with the world. And I think the braver you are, the more brutally honest you are," Taylor shared.

She then fights back tears as she announced Maya is in the building and shares that she read Maya's blog every single night. The blog became all too real to Taylor after her mother was diagnosed with cancer.

So she wrote the song, "Ronan."

Taylor made Maya the co-writer of the song because of the blog. All of the proceeds of the song will go to the Ronan Thompson Foundation. It's a song she rarely plays. In fact, the last time she played it was for Ronan, himself.

You can see the effect the song still has on her in the video. I couldn't imagine there was a dry eye in the building.