Isla Tansey, from Hinckley in Leicestershire, passed away from spinal cancer last year aged seven.
The little girl loved to paint stones and leave them for people to find, painting the hashtag #islastones and the instructions ‘photo, post, rehide’ on the back.
Finders were encouraged to take a snap of the stone, or pose for a selfie with it, before sharing it on social media.
Isla’s mum, Katherine Tansey, said, ‘For some incredible reason, the Isla Stones movement has connected with so many people, people who never met Isla but feel they know her.’
Isla was diagnosed with cancer in 2017 after she woke up one morning unable to walk.
The little girl had already come through a major health battle after suffering from sepsis in the days after her birth.
But aged six her family were told their ‘Isla Smiler’ was suffering from diffuse intrinsic pontine glioma (DIPG) - a rare tumour on her brain stem at the top of her spine.
After surgeons removed as much of the growth as they could, Isla underwent six weeks of radiotherapy.
However the treatment was designed to extend her life, with the childhood cancer found to be incurable.
After months in hospital, Isla began painting stones with her big brother Harrison, 10.
‘Isla painted anything colourful, fun and happy – like her,’ Katherine said.
Then Isla started a Facebook called #islastones with help from her aunties Jackie and Laura, and family friend Sally.
If someone found a stone, they could share a photo in the group.
But soon strangers were joining in, and stones were being found as far afield as Australia, New York, India and even the Antarctic.
The stones became a way of raising awareness about DIPG, and after Isla passed away the movement continued to grow.
Now, there are more than 65,000 people in the Facebook group and stones have been found in 149 different countries.
So far, #islastones has raised an incredible $145,000 for DIPG charity Abbie’s Army through donations and fundraising events.
Katherine said: ‘Nothing will ever replace our Isla Smiler, but to see something positive come out of something so horrific is lovely.’
To find out more search #islastones on Instagram and Facebook.
Support Abbie’s Army by visiting www.justgiving.com/islastones