Know thyself and you will know the universe, said the ancient Greeks. One way to do that now is DNA analysis.
Just put 2 milliliters of saliva into a container, and send it to a DNA testing company. After 20 days, you will get an online report telling you about your ancestry, physical features, risk of disease, and physical and psychological characteristics.
Such testing was invented in the West and is becoming popular in China.
A recent survey by China Youth Daily showed the country has more than 230 DNA analysis companies, and 70 percent of them provide such services. Dozens of new companies have sprung up in the multi-million-dollar industry since 2017.
Celebrities' posts of their DNA reports on social media attract hits and fans, and make headlines across the country.
Zhang Qian, 30, says worsening health drove her to get an analysis.
Work pressure had strained the civil servant's health for many years. Zhang said she had problems with her blood vessels, thyroid and ovaries. In recent years, news of young people dying at work had scared her.
Expecting it to predict and prevent diseases, she paid 699 yuan (about 101 U.S. dollars) for a test in March, which suggested that she was very likely to suffer cardiovascular disease.
Many diseases are caused by genetic mutation. DNA testing can help identify disease or risk genes, so that people can seek treatment.
Qin Yu, 25, an IT company worker, was scared when a test showed she had very high risk of breast and ovary cancer. She recalled Hollywood star Angelina Jolie, who in 2013 had undergone a double mastectomy and later removed her ovaries, after learning that she carried a gene mutation linked to breast and ovarian cancers.
Qin immediately went to hospital for an examination, which found no serious problems. But still upset, she bought health insurance.
In China, DNA testing services are priced from hundreds to thousands of yuan, and getting cheaper.
The cost of testing was 10,000 times higher in 2001, when the world's first human genome sequence map was completed, said Guo Tingting, founder of GeseDNA Technology, a Chinese startup.
"It is no longer a luxury, but a service for general consumers," said Guo.
More than 5,000 genes can be detected, including almost 4,000 genetic diseases, more than 100 disease risks, about 100 types of drug sensitivity and dozens of physical characteristics.
However, most direct-to-consumer testing products provide only limited information about an inherited condition.
Some advertising for DNA tests has been criticized for exaggerated and inaccurate messages about connections between genetic information and disease risk.
But most companies claim that their test results cannot be used for clinical diagnosis.
Human traits and diseases are the result of a combination of genes and environment, said Chen Gang, founder of gene testing company WeGene.
"Even gene expression is affected by the environment," said Chen, adding that genes were not the only factor and some criticism were unfair.
Guo Tinging agreed: "The genetic information is like your background color, together with your experience in life and your surroundings growing up - the factors that jointly decide who you are."
Guo's company focuses on behavioral genetics. Most of its workers, including Guo, have studied neuroscience and psychology.
Her company provides information about people's emotions and behaviors, such as whether you are a party animal, sleep later or a loner.
Some compare such tests to horoscopes.
But Guo said all test results are based on real research published in international journals.
For example, the "ability to fall in love" was based on a study conducted by researchers from Beijing Normal University. They found that most single people with a variant of HTR1A gene easily get stuck or run out of words during an argument.
"Such problems might make it difficult to express their emotions in a relationship, so genes may be an important reason for being single," said Guo.
"It's easy for people to understand that genetic diseases are related to genes, but difficult to understand the way they talk or react to people can also be genetic."
The industry is growing rapidly, but insiders say business is difficult and educating consumers is a long process.
Some people are aware of the benefits.
"If a DNA test suggests you may suffer from lactose intolerance or have a risk of diabetes, nutritionists could help by offering dietary recommendations," said Gu Zhongyi, a popular nutritionist with thousands of followers online.
He is a determined supporter and has tried several tests so far. "Some DNA reports are very amusing, especially when they show some body or behavioral characteristics that you never notice."
Many companies have cooperated with nutritionists like Gu or fitness instructors to draw customers by selling weight-loss and nutrition tips.
Guo's company plans to work with dating websites to develop services, such as introducing customers to those with similar genes.
She expected testing would inspire positive changes in people's lives.
"At the beginning of computer age, people thought computers were just for work, like people today think DNA testing is only for treating diseases," said Guo.
"But today, computers have many functions, so I believe DNA testing can do more too."
