In September 2010, at the age of 15, Stephen Sutton was diagnosed with terminal cancer. It started as a tumor in his bowel, but soon spread to his knee, lungs and liver.
But where many people would have given up hope and resigned themselves to their fate, the teenager from the British town of Staffordshire resolved to turn a personal tragedy into something positive.
That's how "Stephen's Story" came about - an initiative aiming to "spread as much positivity as possible and ...show people what it's like to have something go wrong in your life but not to be defined by it."
Initially, Stephen drew up a list of 46 things he wanted to achieve in his life - from sky-diving to crowd-surfing in a rubber dinghy - but soon realized that his positive energy could be used for something even more important. Rejecting offers to donate money to his cause to help him fulfill his list, he decided instead to give it all to charity.
His first £10,000 donation to the Teenage Cancer Trust eventually became more than £3 million. As of this evening, Stephen's Story has raised nearly £3.5 million ($5,874,050).
But just as importantly, his infectious positive energy and unstoppable drive to make the world a better place inspired countless others to do the same.
And despite enduring one grueling treatment after another, he never lost that energy - using his Facebook page to communicate with his rapidly-growing base of followers with a sense of humor which, considering the circumstances, was nothing short of humbling.
His final message, posted when he was admitted to hospital just three days ago for the last time, was a case in point:
"Unfortunately today I've ended up back in hospital! I had some breathing difficulties starting last night and after going to A and E have been admitted back to a ward for monitoring. I've still got the cough, then quite quickly developed a wheeze in my breathing and breathlessness upon any physical exertion.
"There's no immediate panic and I'm currently quite stable- I have been put on nebulisers and other meds which are currently helping my symptoms hugely. The doctors think there may be something restricting my airway again, they're not sure exactly what yet though(tumour regrowth, infection, inflammation, etc are all potential reasons mentioned), but are currently discussing the possibilities and my scan results to decide what to do next.
"The whole thing is very inconvenient aha. I had a few cool things planned to attend today, then tomorrow was due to appear on the telly on BBC Breakfast News! I understand my health is the obvious priority though and have had to cancel. Fingers crossed the issue will be resolved and that I'll be out of hospital soon, I'll keep you all updated with how I'm getting on"
Two days later his family posted a message saying his condition had worsened to the point that he was unable to communicate.
This morning, his mother informed his more than one million followers that her son had passed away aged 19.
"My heart is bursting with pride but breaking with pain for my courageous, selfless, inspirational son who passed away peacefully in his sleep in the early hours of this morning, Wednesday 14th May. The ongoing support and outpouring of love for Stephen will help greatly at this difficult time, in the same way as it helped Stephen throughout his journey. We all know he will never be forgotten, his spirit will live on, in all that he achieved and shared with so many."
Tributes poured in, with British Prime Minister David Cameron Tweeting: "I'm deeply saddened to hear that Stephen Sutton has died.
"His spirit, bravery and fundraising for cancer research were all an inspiration."
Opposition leader Ed Miliband echoed those statements, saying "His bravery & determination to live life to the full was an inspiration to us all."
Stephen had said that he didn't want to measure life in "terms of time but by what I actually achieve."
By that measure, he lived as full a life as anyone.
That is Stephen's Story.