Tian Li was born in the summer of 1986 in southeastern China's Guizhou Province. His father, then 27, took the first photo with him on his birthday. Courtesty Tian Li

Tian Li, 29, is a director living and working in Beijing. He told CNN that his artist father Tian Jun, 56, had the idea of taking a picture every year on his son's birthday in the same spot. Courtesty Tian Li

Tian, the son, recalled that most of the photos were taken against the wall outside of the apartment where the family had lived together for 20 years in southeastern China's Guizhou Province. Courtesy Tian Li

Tian told CNN the reason why they were shirtless in pictures is because Tian Li's birthday is in the summer. "The weather was so hot so we went bare-chested. We've kept the ritual consistent deliberately." Courtesy Tian Li

Tian Li said he had never thought about what the photos meant to him when he was younger. "It has become a habit a long time ago that we took the same picture every year when I visited my parents, as naturally as going home for the Chinese New Year's Eve dinner every year." Courtesty Tian Li

Tian Li was born in 1986. Courtesy Tian Li

His father was born in 1959. Courtesy Tian Li

Tian Li sees the series of images as a form of performance art rather than just photography. Courtesty Tian Li

As his son grew up, his dad grew older and gained weight! Courtesy Tian Li

Tian Li posted the photos to Chinese social network WeChat, and the images have been viewed by millions around the world since late July. Courtesy Tian Li

Tian acknowledges that the story of father-son bonding, and a boy's coming of age, have a universal appeal. Courtesy Tian Li

The last year Tian Li was carried by his father in the photo. Courtesy Tian Li

Tian Li says his dad ran every business you could think of, from real estate to tourism to farming, before returning to the art school he had taught at for years. Courtesy Tian Li

Teenager Tian Li, 13, with dad Tian Jun, 40. Courtesy Tian Li

A puppy joins them in the picture. Courtesy Tian Li

Sixteen years in, the photo became more casual than ever. Courtesy Tian Li

Tian Li at 16, Tian Jun at 43. Courtesy Tian Li

Bill posters occupied the background. Tian Li grew taller than father Tian Jun this year. Courtesy Tian Li

Eighteen-year-old Tian Li was admitted to Beijing Film Academy. Tian told CNN this year marked the first and biggest milestone in his life. He has since left home and pursued a career as a film director in Beijing.

But the Tian family's photo ritual continued. Tian Li said they took the pictures when he visited his parents during the summer breaks. Courtesy Tian Li

Tian Li turns 20, his father 47. Courtesy Tian Li

Tian Li graduated from college with a degree in Film Directing. This picture was taken inside his parents' home in the winter. Courtesy 22

Tian Li at 22, Tian Jun at 49. Courtesy Tian Li

Tian Li at 23, as Tian Jun turned 50. Courtesy Tian Li

This year, Tian Li went to graduate school to study more directing. Courtesy Tian Li

Tian Li turned 25, while Tian Jun was 52. Courtesy Tian Li

Tian Li got married. Courtesy Tian Li

Tian Li is carrying his father in this picture. Courtesy Tian Li