As the 20th anniversary of the June 4 demonstration approaches, Tiananmen still remembers the cruel crackdown on pro-democracy protesters. Hundreds of people were killed on June 4, 1989.

Nowadays China security forces blanketed Tiananmen Square on Wednesday, a day after Twitter and other Internet services were blocked in China.

I don't think June 4 has been forgotten, but under pressure of fear, people are afraid to speak out, said Yu Jie, a writer in Beijing.

They are scared there will be a big blow-up because of tomorrow, but I don't think anything will happen, Yu said the tight security showed that memories of 20 years ago remained politically volatile.

Tiananmen Mother still remembers clearly what had happened to their sons and daughters.

One mother, Ding Zilin, a retired professor still clearly remembers her son's death and is calling on the Chinese government to reassess its officially upheld verdict that the demonstrations were counter-revolutionary.

Everything seems like it just happened yesterday, Ding said. “To me, this trauma has never faded as the time passed. The sorrow and pain gets stronger each year, as I get older.

Ding's son was shot as he and a classmate hid behind a flowerbed, near Building 29, near the area of Beijing known as Muxidi.

Ding's son was cremated on June 7. She keeps his ashes at home, along with a fragment of the Berlin Wall, which came down the same year.

She says her son and young Germans shared some of the same vision. These are universal values, she said. They both were pursuing freedom and democracy.

Ding is one of the best known members of a group known as Tiananmen Mothers, made up of parents whose children were killed in the 1989 crackdown.

She says the Tiananmen Mothers share the same basic principle - opposition to the use of violence.