The inside story of the tech entrepreneurs who created the social media app Twitter. At first the site grew on the back of celebrities who realised it offered them a direct way to communicate with fans. After going global, it seemed to be fulfilling the founders' dream of a digital utopia where all voices would be heard. But as hate speech and misinformation flooded the platform, the founders faced growing problems to control it - and the sale to Elon Musk in 2022 represented the end of their dream.