The world was shocked when Selena Gomez revealed that she had secretly undergone a kidney transplant over the summer due to complications from lupus. Her donor was none other than her best friend, actress Francia Raisa, whom she publicly thanked for her selfless act on Instagram

“There aren’t words to describe how I can possibly thank my beautiful friend Francia Raisa,” Gomez wrote. “She gave me the ultimate gift and sacrifice by donating her kidney to me. I am incredibly blessed. I love you so much sis.”

Gomez teased that she would be sharing more about what she went through with her fans, and now she's following through by opening up about her and Raisa's journey in a new interview with NBC's TODAY

In a preview of the sit-down released on Friday, a tearful Gomez revealed just how close she was to death before Raisa stepped in.

"My kidneys were just done, that was it," Gomez told TODAY.

Gomez didn't want to ask anyone for a donation, but Raisa — who has been in her life since they met at a children's hospital visit organized by Disney and ABC Family almost a decade ago — volunteered.

What an incredible friend!

She feels that Raisa saved her life. “Because she did. That’s it,” she said. “I guess I got to the point where it was really kind of life or death.”

We had no idea just how serious Gomez's situation was. The fact that Raisa made such an enormous sacrifice for her bestie is a huge testament to their incredible bond.

You can catch the full two-part interview with TODAY when it airs on NBC next Monday and Tuesday, and see the preview below.