It's the end of class. When the bell rings, students of Luohu ForeignLanguages School in Shenzhen quickly take out their cell phones.
They want to log on to their micro blogs to check the interesting things that have happened in the last hour.
   Since last year, the trend (潮流) of micro blogging has swept the country. Recent surveys shows that most students in middle schools have a micro blog and some even update their blogs over five times per day.
   "We learn many fresh and interesting things on micro blogs and they have become popular topics in class," said Andy Liang, 14. "If you do not know about them, you are out of the loop."
   It is also a great place for students to let out stress. "My parents always ask me to study hard, and encourage me before exams, but it really adds pressure," said Simon Zhang, 15. "When I share these feelings on my micro blog, I get many replies from friends in the same situation, which makes me feel better."
   But parents are worried that micro blogging could be a waste of time. Some misleading messages may even cause danger to kids, they said.
   Mr. Shen, a professor at the China Education Association, suggests parents not worry too much as long as kids are not crazy about micro blogging. Maybe it can become a window for parents to understand their children.
   "If parents can read their children's micro blogs, they'll know their thoughts, thus leading to better communication and solutions to problems," he said. He also gives some tips for kids.
   -Don't micro blog for more than one hour a day.
   -Never micro blog in class.
   -Try to talk face to face with people from time to time.
   -Be critical(批判性的). Don't trust all the messages on a micro blog.

Nearly all American students in colleges and universities pay for their education. There are many expenses. First of all, there is tuition (学费). At some schools, the tuition is very high, ten thousand dollars a year or more. At other schools, it may only be a few hundred dollars a year. At some community (社区) colleges, tuition is free. There are other expenses as well. Many students leave their homes to go to schools in other cities. They may live in dormitories or apartments (flats), and they must pay for it. Finally, students must buy textbooks for their courses. Some families start saving money for their children's education when the children are small. Many students work to save money for tuition. They can also get loans (贷款) from the government. They pay the money back to the government when they finish their education.

    Silk production has a long history and colourful history unknown to most people. Scientific discoveries have shown that silk production began in China around 2,500 B.C., although it could be much older. For hundreds of years, China kept the secret of silk to itself as one for the most closely protected secrets in history. Anyone telling the secret of silkworms or trying to take silkworm eggs out of ancient China was punished in prison.

    At one time silk was served only for the Chinese emperor. Step by step, others began wearing silk. In addition to being used for clothing, silk was used to make musical instruments, fishing lines, ropes and even paper. During the Han Dynasty silk became a form of money.

    However, the Chinese finally lost their monopoly(垄断) on silk production. It reached Korea in around 200 B.C. when some Chinese people arrived there. Silk production came to India in 300 A.D. In 500 A.D., silk production came to Europe when travelers smuggled(偷运) out silkworms in empty pipes of bamboo. These were used to set up silk factories in Rome, although Chinese silk was still considered to be the best.

    Silk was brought to Rome from China by means of the Silk Road. There were actually two Silk Roads, one over land and one on the sea. Especially the land route had a huge effect in history. All sorts of trade goods were passed along this road. Ideas travelled the Silk Road, too. For example, the religion of Buddhism(佛教) was carried to China from India by traders on the Silk Road. The Silk Road created the first international culture, showing many people the ideas and treasures of both Western and Chinese cultures.