In a black-and-white photo, a fist presses on the table, nearly covering the entire frame. The fist belongs to Taotao, a 6-year-old boy with Type 2 spinal muscular atrophy.

Taotao is featured in a photo exhibition, entitled Angel's Smile, which displays 40 photos centering on children with SMA2, a genetic neuromuscular disorder that affects the nerves that control muscle movement. It's hard for children with the condition to stand up and walk. It also affects other parts of the body, causing muscles to become weak and shrink.

The photo exhibition is being held at the No 1 Cultural Center of Xicheng District in Beijing until Dec 13.

"Taotao's hands are the only parts of his body that he uses to support himself. He uses his hands to also hold books, read and write," says photographer Sun Ke, who drove hours to visit the little boy and his family in a small village in the city's Yanqing district to take the pictures.

Since the boy's parents work in downtown Beijing, Taotao's grandmother takes care of him.

"There is a small garden outside their house, and the grandmother takes Taotao out in a wheelchair every day," says Sun, who has also taken photos of her.

Taotao is one of the four children featured in the exhibition.

Sun spent over three months visiting families of children with SMA2 and taking their photos. The project was quite challenging for the Beijing-based photographer, who has been working as an independent photographer since 2009. Sun knew nothing about SMA2 until he prepared for the exhibition, so he had to do a lot of research.

"I started to communicate with the families online before I actually visited them. Some of them are very shy and were reluctant to talk about their children while some are open-minded and were willing to share their stories," says Sun. "I took thousands of photos in three months."

Sun tried to give the children his camera to get close to them but found they couldn't control their fingers.

"It seems to be very simple and easy to press the shutter button, but it was almost impossible for them," says Sun.

Songzi was Sun's first interviewee. The 7-year-old boy in Beijing has used a wheelchair since he was 18 months old. Songzi smiles and plays with his grandparents. In one picture, Sun captured the moment when Songzi sat in his wheelchair while looking out of the window and the sun's rays fell on him.

In 2017, Sun made children with hearing impairments the subject of his photos.

"Usually, major diseases are associated with misery, but I don't want to show the misery. I want the photos to be bright and full of hope, which brings people strength," says Sun.

Sun was invited to work for the Angel's Smile photo exhibition project by the dancer-choreographer Liu Yan about six months ago.

Considered one of China's leading classical dancers at the peak of her career, the 37-year-old severely injured her vertebrae during a rehearsal for the opening ceremony of the 2008 Beijing Olympics. The accident left her paralyzed below the waist, and she had to bid farewell to the stage and adjust to life in a wheelchair. However, this didn't stop her from continuing to dance and trying to push the boundaries of the art form.

After withdrawing from the limelight, Liu established the Liu Yan Arts Special Fund in 2010 to help students living in poverty, orphans and migrant workers' children through arts education.

Liu is now devoted to dance-movement therapy as a professor of the Beijing Dance Academy,.

She and the China Literature and Art Foundation initiated the Angel's Smile photo exhibition in 2011, when the focus was on children with hearing impairments, orphans and children with rare diseases.

Liu says she got the idea for this year's exhibition after some children with SMA2 attended her dance class.

"The children opened their hearts while dancing," says Liu, who was born in Hohhot in the Inner Mongolia autonomous region and has studied classical Chinese dance since age 9.

She graduated from the Beijing Dance Academy in 2003. She won national awards and appeared at galas as a solo dancer.

"We want more children with diseases to benefit from dance," Liu says, adding that dance therapy is not just for children but also their parents, who need to relieve stress and stay healthy.