Liu Jude, a professor at Tsinghua University's Academy of Arts and Design and a former student of Zhu Danian, went with him on several sketching trips. He says that, while students felt daunted by the overwhelming details of a landscape they were to draw, Zhu Danian "felt intrigued by the layers upon layers of trees, woods and forests and the complex, changing scenes in which he found the true beauty of nature".

"I remembered he once climbed up to the rooftop of a farmer's house, so that he could have a clear view of two date trees. He sat there for a whole day, so focused on the scene before him. His mind clear and his fingers steady, he drew the twisting and interweaving tree knots and branches with sweeping meticulousness," Liu says.

"The next day he continued to draw on the rooftop, and added a paddy field and shepherds. Two decades later I saw the drawing at an exhibition, and still, I felt invigorated and moved."

Zhu Heng, the grandson, says people often say how much they admire Zhu Danian's hardworking spirit, but he didn't feel tired even after working outdoors for hours.

"When he was devoted to what he was doing, he enjoyed the process, not realizing how long he had been sitting there and painting, and not caring about how many papers he had used and thrown away."

Zhu Danian's depictions of Xishuangbanna give a full expression to his enthusiasm for the place's distinctive tropical views and diverse ethnic cultures. The works enthrall people with lively details in which the artist endowed a profound take on all life on Earth.

When he was commissioned to create a mural to decorate a restaurant at Beijing Capital International Airport in the late 1970s, he designed a ceramic piece that showed a panoramic view of Xishuangbanna's tropical forests, waterfalls, rivers and a boat carrying five people of the Dai ethnic group in Yunnan. He was also inspired by a 380-year-old great banyan in Jiangmen, Guangdong, known as "birds' paradise".

The monumental mural, titled Song of the Forest, measures 20 meters in length and 3.4 meters in height, and comprises more than 3,000 ceramic tiles, made with the aid of artisans in Jingdezhen, Jiangxi province, hailed as China's "porcelain capital".