Despite their unusual materials and large size, Gu's art has found an increasingly broad audience, even in China, which he left for the US in 1987. He joined dozens of avant-garde mainland artists who emigrated at about the time of the Tiananmen Square crackdown and created a contemporary Chinese art movement. Gu is one of the best known of the movement's artists, along with such well-known names as Cai Guoqiang, Chen Zhen, Huang Yongping and Xu Bing.

In 2001, Gu had his first survey exhibition at the National Gallery of Australia, in Canberra, a sign of acceptance by the mainstream art world. 'Wenda has gone beyond being a diaspora Chinese artist and really made a place for himself in a very difficult contemporary art scene,' says Robyn Maxwell, the gallery's senior curator of Asian art. 'We think he's one of the important artists of the late-20th and early-21st centuries. The interest is in his themes, the way he's able to transcend those national boundaries and offer a way of creating art that's truly international.'

An exhibition of several of Gu's major works, including United Nations: United 7561 Kilometres, a tent-like structure composed of a single braid of hair that would stretch to 5km if flat and 7,561km if made to form a single strand, is touring to four university museums in the US. Accompanying the exhibition is a recently released book with the same title, Wenda Gu: Art from Middle Kingdom to Biological Millennium, which tracks Gu's progress from sinocentric work to an obsession with biological materials and genetic engineering. In mid-2005, the exhibition will move to the Contemporary Art Centre of Macau and then Shenzhen's He Xiangning Art Museum. Gu is working on another hair piece that will be part of a group show on the Great Wall, to be held at Beijing's Millennium Dome, at about the same time. The work will require four tonnes of hair (obtained from a hair-recycling plant near Shanghai) and will represent a section of the wall, built from hair bricks.

For a preview of Gu's work, you can catch an installation of neon letters in an invented calligraphy at Hanart TZ Gallery's 20th anniversary show, from Friday until May 2 at the Hong Kong Arts Centre. 'He was one of the first artists to come up with the idea of using wrongly written words and breaking the taboo of correct script form in order to create a kind of iconographic power,' says Hanart TZ founder Johnson Chang Tsong-zung. 'He's always rather fearless in being provocative of cultural and political issues wherever he goes - not just in China but in America and other parts of the world, picking on scenes sensitive to the native culture.' The gallery has sold about 50 Gu pieces over the past 15 years, from ink paintings to larger installations; prices for his work range from US$12,000 to US$400,000.

Hair seems to arouse curiosity more than disgust. Gu first delved into hair in 1993, when he launched his United Nations series, which now consists of 23 monumental installations; the largest is 25 metres tall. A utopia of seamless ethnic blending is the message here, one that has been enthusiastically received around the world. The series has toured to 18 countries, where about 1.5 million people have donated their hair to the project.

Gu divides his art career into three phases. The first involved experiments with language in China in the 1980s. He produced giant ink paintings with ancient poems in fake and real characters as well as huge three-dimensional installations weaving together elements such as wood, bamboo and cotton. At the China Academy of Art in Hangzhou, where Gu taught classical landscape painting, he covered the walls and floors with the ink paintings and - in what he says was one of China's first performance-art acts - delivered a wordless speech, complete with animated gestures. 'He questioned two significant cultural icons, calligraphy and landscape,' says Christina Chu Kam-leun, chief curator of the Hong Kong Museum of Art.

Gu's ink works alarmed the propaganda department in Xian, where they were about to be displayed in his first solo show, and the government closed the show before it opened. 'They suspected some political message behind the unreadable calligraphy, but actually, it was just about the philosophy and nature of language,' Gu says. 'This was so different from traditional ink painting, they thought it was revolutionary and suspicious.'

Gu's second phase started with his arrival in the US until the early 90s. 'I abandoned language because I didn't think it could convey the truth of the planet,' says Gu, disillusioned by his struggles to master English at the time. 'I thought language had limitations.' His focus turned to materials, and he created several pieces of outdoor art, including one in Aix-en-Provence, France, and another in Fukuoka, Japan. He also made installations using grass and acrylic.

In the 90s came the revelation that defines his work today. 'The most essential material isn't objective material - it is subjective material, which is the human being,' says Gu, whose own hair is 60cm long. 'I present the human self, not a representation of the human. The human body, the hair work - it's like a mirror. It closes the gap between the work and the viewing audiences.' Enigma of Blood, Gu's menstrual-blood series, includes statements from 60 women from 16 countries who mailed Gu their used tampons. Each 'donation' was displayed in a glass box with two white pillows for the statements and the tampons. The series aroused strong feelings, polarised between love and hate. 'The Taiwan people put an advertisement in the paper: 'Women wanted to donate menstrual blood to this project',' Gu says. But the main sponsors of the Museum of Contemporary Art in Sydney withdrew their funding for a year; viewers called the museums to protest; exhibits were cancelled. Newspaper critics asked: 'is it art?'

The series travelled to Hong Kong, Australia and the US between 1993 and 1995. 'I never do anything just to create controversy, but I thought it was a good thing to stir people's minds and thoughts,' Gu says.

For his placenta series, Enigma of Birth, Gu enlisted a friend who worked in a maternity hospital in China. The placentas - from normal, abnormal, stillborn and aborted foetuses - were ground up and displayed on beds covered with glass; one bed, labelled 'aborted', remained empty. Viewers in the west reacted vocally - to material that is emotionally charged and politically symbolic in their culture.

Most of Gu's United Nations works have been commissioned by institutions that then dispatched assistants to help collect hair from salons. Hanart TZ commissioned United Nations: Hong Kong Monument: The Historical Clash in 1997 to commemorate the handover. The work consists of a Hong Kong flag fashioned from Chinese hair, a British flag of British hair and, scattered on the floor, Hong Kong hair mixed with rice and dried poppy flowers, symbolising China's humiliation by the British after the Opium wars.

Gu's performance art examines some of the same issues, such as identity and culture clash. In Wenda Gu's Wedding Life, performed at some of his shows' openings, he stages a mock wedding in which he marries a man or a woman of another race. Gu and his intended write their biographies on rice paper from left to right and right to left until they overlap and blend into one, creating an ethnic meld similar to that suggested by the hair art.

Gu also has a studio in Shanghai and another in Xian. He visits the mainland to supervise the assistants' work and see his parents in Shanghai and his son, 16, in Hangzhou. Gu and his first wife are divorced; he married interior designer Kathryn Scott in 1999.

Gu says he has 15 projects in the works, which will continue, of course, to raise the issues of culture and identity. As for his own, the artist, a Chinese citizen, says: 'I'm always a Chinese artist. The different passports change your identity very little. My goal is not about identifying my ethnicity but to define whether I'm a good artist.'