This is where the superhero sleeps.

Aaron Hunter's bedroom has sky blue walls and a window ledge lined with his favourite toys.

An Iron Man figurine stands guard next to Captain America and Spiderman, all grouped together around Aaron's oxygen tank.

The same faces decorate the headboard of his bed nearby, rows of stickers of the heroes he fights alongside in his dreams. Sometimes they chase down bad guys together, the ones trying to destroy the world.

On other nights, after a particularly difficult day, Aaron dreams that he is out with them trying to save other children who are fighting an invisible bad guy just like he is.

When he was a toddler, Aaron was diagnosed with one of the rarest illnesses in the world. ROHHAD, a life threatening condition, causes rapid weight gain and breathing problems in young children.

The chances of Aaron developing it were one in 73 million.

It meant that he went from a healthy little boy full of energy, to a child confined in a wheelchair relying on a ventilator to breathe.

A notably cruel and complex disorder, ROHHAD severely impacts on a child's quality of life. For many sufferers, the condition can be terminal and children living with it face a daily fight for survival.

ROHHAD stands for Rapid-onset Obesity with Hypothalamic Dysfunction, Hypoventilation and Autonomic Dysregulation.

There is currently no known cure and no significant funding for research into finding one.

At just eight years old, Aaron is running out of time. He is not, however, running out of heart.

This year, he has proudly worked with his family to design a Zero to Hero campaign, encouraging people all over the world to take on a sporting challenge to raise awareness of this condition and fundraising for much needed research into a cure.

Set to launch in May 2018, he was inspired to ask people to carry out a sponsored distance they would like to complete during that month.

"He had always wanted to be part of the Daily Mile school campaign which gets kids active," says his mother Elisabeth.

"For Aaron though, that is a massive distance and he can only go a couple of steps without oxygen."

Aaron felt left out and knew others might too. One mile might seem a small challenge to some people. For others like him, one mile could feel like the toughest journey in the world.

"His goal was to come up with something anyone could do, with a wheelchair, on foot, in water or even with a carer," says Elisabeth.

If enough people take part, Aaron is convinced that a life could be saved.

Over the last year, he has already had to say goodbye to two of his young ROHHAD friends, losses his mother says he found devastating.

Several schools across Scotland have said they are keen to sign up, to Aaron's delight, as have a few famous Paralympics including Scots cycling hero David Smith.

''After hearing about Aaron and watching his video on the ROHHAD association website I was honoured to be involved in ZERO TO HERO during superhero month," says David.

"No child should have to face this alone and by raising awareness of the condition we can not just support Aaron but all the Children who face this challenging condition.

"Having a rare condition like ROHHAD is a tough card to have in life as people don't understand it and you sometimes feel lost and alone, I have huge empathy to what Aaron faces with more questions than answers, it is very humbling how positive the little guy is.

"I encourage you to sign up to zero to hero and make a positive difference to these children's lives. ''

This is the second campaign that Aaron has spearheaded in an attempt to raise awareness.

Last year, the brave boy from West Dunbartonshire launched a charity "puddle jumping" campaign to also raise money for ROHHAD research.

He even managed to convince First Minister Nicola Sturgeon to jump in a muddy puddle for him.

There was also one other particularly special person he managed to get involved.

Aaron had watched many a superhero movie in his young life, and he knew that as good as doctors are, sometimes a hero needs to fly in and give a helping hand.

Which is why he asked his mother for paper and a pen so he could sit down and write to his favourite hero of all.

Dear Iron Man,

Can you please help me and my friends who have a very bad disease, Rohad?

We don't get any help to find a cure from the government, cause there are only 100 of us, we are too rare.

Some of my friends have died and I don't want any more of my friends to die. Please help me and my friends.

Love Aaron Hunter

6 years old

Captain Braveheart

He covered the paper in superhero stickers and gave it to his mother to post.

Weeks went by and he didn't hear anything back. So he decided, with the help of his big sister Lauren, to put up a video of him reading his letter.

It went viral. Avengers fans across the globe began to share it, trying to flag it to actor Robert Downey Jr.

Within weeks, Aaron received a special video call. It was from the Hollywood star.

Videoing in from California - in full character as Tony Stark - he told his young fan what a "brave hero" he was.

"He was in character as Tony Stark and Aaron absolutely believes that he has spoken to the real Iron Man," Elisabeth says.

"To him the characters are real, he doesn't quite grasp the whole actor thing. He doesn't know of Robert Downey Jr, he just believes there's a Tony Stark.

"He believes so much in them and I don't want to take that magic away from him, especially now with everything he's going through."

Months on, and Aaron is still beaming, even though physically things are getting tougher.

After a difficult time coping with Scotland's winter weather, he is now frequently housebound for his own health.

His small body plummets into hypothermia without warning and alarmingly, he stops breathing when he asleep. His ventilator - which he calls his Iron Man mask - has to step in and breathe for him.

On the really bad days, his mother is there, with superhero movies and emergency marshmallows.

But always, she says, his smile is there.

"He's very excited about his new campaign and he's going to wear a superhero cape at the launch in May," says Elisabeth.

"He really believes this could help his friends, and he's very excited at the idea of being able to cross a finish line for the first time, dressed in his cape, with all his classmates."

Though as Elisabeth knows better than anyone, not all superheros wear capes.

Some of them are small children, wrapped in bed sheets, carrying an oxygen tank and the biggest heart in the world.

You can find out more about the Zero to Hero challenge here online.