Claire Wineland, a social media star and cystic fibrosis activist, has passed away after a successful lung transplant. She was 21 years old.

The young woman was taken off of life support on Sunday, Sept. 2, after suffering a massive stroke shortly after her surgery. The news was confirmed by Claire's Place Foundation on Facebook.

"Our inspirational founder passed away," reads the post. "She was not in any pain and the medical staff said it was the most peaceful passing they had ever witnessed."

Her organs were made available for transplant.

Who Was Claire Wineland?

Last year, Wineland started a YouTube channel to talk about her experience, specifically her struggles with cystic fibrosis. Since then, she gained over 250,000 subscribers. However, in 2017, she had to leave the platform because of her health.

Thousands of fans followed her on Twitter and Instagram where she continued to talk about her illness, share life experiences, and advocate for patients with similar diseases.

She founded Claire's Place Foundation when she was 13 after waking up from a medically-induced coma. The foundation gives financial and emotional support to families affected by cystic fibrosis.

She also authored a best-selling book titled Every Breath I Take: Surviving and Thriving with Cystic Fibrosis.

In July 2017, the late social media star did a TEDx Talk called "Don't wait to be healed to start serving humanity," where she discussed in detail her illness and experience with treatment, the life expectancy of patients with cystic fibrosis, and setting up her foundation.

"You can suffer and still make something," she told the audience at the time. "That the quality of your life isn't determined by whether you're healthy or sick or rich or poor, not at all, it's determined by what you make out of your experience as a human being, out of the embarrassing moments and the painful moments. It's what you make and what you give from that place."

What Is Cystic Fibrosis?

Cystic Fibrosis is a progressive, genetic disorder that affects the cells that produce mucus, sweat, and digestive juices. It can cause severe damages to the major organs of the body, including the lungs and the digestive system.

A double lung transplant, the surgery that Wineland had undergone a week before she passed away, could alleviate symptoms and extend a patient's life.

More than 30,000 people in the United States and an additional 70,000 worldwide were diagnosed with cystic fibrosis, according to the Cystic Fibrosis Foundation. Until now, no cure for the illness is available.