The BBC's Chinese Service asked people to share some of their thoughts and recollections about China's Tiananmen crackdown 20 years ago today. Anchor Lisa Mullins introduces us to two of them.

Hong Kong vigil for the victims of the 1989 crackdown

Twenty years ago today, Chinese troops cleared Tiananmen Square. Hundreds, possibly thousands of people were killed in and around the square. Chinese students had been calling for democracy and free speech. The World's Mary Kay Magistad reports from Beijing on an ongoing legal dispute over a documentary about the 1989 Tiananmen crackdown called "The Gate of Heavenly Peace". The case pits the filmmakers against one of the student demonstrators.

The answer to today's Geo Quiz is Cedar Rapids, Iowa. The city is home to the Mother Mosque of America, an Islamic cultural center that is one of the oldest mosques in America. It's one of the approximately 1,200 mosques in the United States that President Obama referred to in his speech in Cairo today.

Twenty years ago today came word of the death of Iran's supreme leader, Ayatollah Khomeini. Journalist John Hockenberry recalls the events surrounding the death and funeral of the Ayatollah. Hockenberry was one of many American reporters covering the story from Tehran.

Anchor Lisa Mullins speaks with Borzou Daragahi, Middle East correspondent for the Los Angeles Times, about reaction in Iran to President Obama's speech, and about last night's presidential debate in Tehran between the incumbent and his main challenger.

The World's Aaron Schachter goes into the streets of Kabul to get reaction to President Obama's speech to the Muslim world.

The World's Katy Clark tells us about how the White House tried to ensure that President Obama's Cairo speech got out to as many corners of the globe as possible.

Anchor Lisa Mullins gets reaction to President Obama's speech in Cairo from Yossi Alpher, co-editor of BitterLemmons.org, an online dialogue between Israelis and Palestinians.

Anchor Lisa Mullins speaks with Tariq Ramadan, a professor of Islamic Studies at Oxford University, and Shibley Telhami, the Anwar Sadat Chair for Peace and Development at the University of Maryland, for analysis of President Obama's speech today in Cairo aimed at the Muslim world.

Anchor Lisa Mullins introduces coverage of reaction to President Obama's speech in Cairo today reaching out to the Muslim world. Reporter Ursula Lindsey spoke with some Egyptians in a Cairo cafe to get their response.

Watch the President's speech in its entirety

President Obama's Cairo Speech: full text with analysis