Following the tremendous success of her concerts in the UK, about which fans and critics sang their praises, global superstar Katy Perry announced that she will set out to Europe in 2015 and will once again perform in 18 countries with her stunning "Prismatic World Tour" program. In 2013, Katy Perry also became the world's most watched celebrity on Twitter, has been named a global ambassador for UNICEF, received nominations for two Grammy Awards (Song of the Year and Best Pop Solo Performance) and also recently won the award for best female singer for the year 2013 at the MTV European Music Awards. Her album PRISM debuted in first place on the iTunes charts in 97 countries. The record achieved the best sales results in the career of the singer. In total the title has sold more than 6 million copies worldwide in the six months since its release. The single ROAR has sold over 10 million copies worldwide and became the best selling single in Canadian history.