HumanKind is a celebration of kindness. We want to tell the stories of people who have done incredible things for others or the planet. Find more uplifting stories from our HumanKind series here.

Families are writing lovely messages on rocks and hiding them around the UK in what is quite possibly the nation’s biggest (and most wonderful) game of hide and seek.

Kindness Rocks is an initiative which started in the US, but soon found its way across the pond. The idea is that people write and draw on pebbles and leave them in hidden locations. Strangers then find the pebbles, feel uplifted and hide them again.

It’s a cycle of positivity which is taking places like Salisbury, Reading, Chester, Tyneside and Norfolk by storm.

“Rock painting is a very accessible and inexpensive activity for anyone and everyone to do,” says mum-of-three Kristina Auckland, who set up Salisbury’s offshoot of Kindness Rocks last year after seeing it take off in the US. “I love that it’s getting people outside and exploring. Seeing the photos on the Facebook group of the proud little faces when they’ve either hidden or found some painted stones is amazing.” 

The groups vary in size: Reading has just over 800 members, Salisbury has 1,300 while Norfolk and Tyneside’s groups operate on another level entirely, with over 37,000 members and 27,000 members respectively. 

One of Norfolk’s members, Karen Harrison‎, took to Facebook to explain how finding a beautifully-illustrated rock with the message “dream” brought her joy during a particularly tough time. She shared her feelings on the group page and received a reply from the person who had illustrated the rock, Polly Johnson, who said she could keep it. “I hope things soon get a bit easier for you,” she added.

Angela Thompson discovered a rock with the message “smiles are contagious” while out walking in the woods with her son and friends. “The weather wasn’t brilliant, so when we saw the rock it made us all smile. You see someone laughing, you laugh too,” she explains. “My son was so excited. It does inspire you to create some rocks with messages on and place them for people to find. You hope it makes someone’s day when they are feeling down.”

Other rocks that have been found dotted around the country feature messages such as “you’re a star”, “I believe in you” or “lots of love”.

The scheme also seems to be sparking a miniature art movement among kids. Kristina explains: “As a lot of the people who are painting the stones are young children, the paintings tend to be more pictures and colours than messages.”

The Facebook pages contain hundreds of photos of kids proudly smiling with the stones they either found or created.

“People have absolutely loved getting involved and taking part,” Kristina adds. “If they are still posting photos of them hiding and finding rocks in a year’s time, that would be amazing.”

If you’re interested in joining in the fun, find your nearest Kindness Rocks group on Facebook or, if there isn’t one, set one up and invite your friends to join.

Next, get hold of some stones. Kristina says palm-sized, smooth stones are the best – especially for little hands. Use acrylic paints to paint the stones with pictures or messages, make sure the rocks are sealed, and use environmentally friendly products if you can. Then, take the rocks and hide them around your local area.

“Post a message in your Facebook group hinting at where the rocks can be found,” says Kristina. “At the same time, hunt around and if you find some painted rocks, take a photo and post to Facebook, then hide it again so someone else can join in the fun.”

Do you know someone in the UK who’s done something incredible for another person? Maybe they dedicated hours to volunteering, changed someone’s life with a small but significant act, raised thousands of pounds for a good cause, or perhaps they went above and beyond to help in someone else’s time of crisis? Either way, we want to hear about them. Nominate your kind person or group here or email your personal story to natasha.hinde@huffpost.com.