#BBCtrending: The Iranian president's surprising tweet

By Sam Judah. The president of Iran has broken new ground by tweeting a photo of a female mathematician without a hijab. His decision prompted a powerful reaction on social media.
The mathematician in question - Maryam Mirzakhani - is Iranian, and recently became the first woman to win the Fields Medal for her pioneering work in the field. President Rouhani tweeted a message expressing his delight at the news. "Congrats to #MaryamMirzakhani on becoming the first ever woman to win the #FieldsMedal, making us Iranians very proud," he said. More...