Mobile messaging app WhatsApp said it has crossed the one billion user milestone globally. In last five months 100 million new users joined WhatsApp. In February 2014, WhatsApp was acquired by social networking site Facebook for 19 billion dollars.In a post on Facebook, WhatsApp co-founder Jan Koum said 42 billion messages were sent, 1.6 billion photos and 250 million videos shared everyday on the platform. He added that there are one billion groups on WhatsApp.In India, more photos are sent using WhatsApp than in any other country in the world, said company statement. Facebook chief Mark Zuckerberg congratulated Koum and his team. Recently, WhatsApp had said, it will not introduce any third-party ads for monetisation and is going to experiment with new models to stay ad-free.