The Twitter story, from first tweet to IPO

Twitter, the 140-character messaging service favored by everyone from the Pope to U.S. President Barack Obama, began as a side-project but rapidly morphed into one of the most powerful social and cultural media forces of our time. After eight years of explosive user growth marred by persistent technical challenges and management shake-ups, Twitter is now preparing to go public in Silicon Valley's largest initial public offering since Facebook Inc's last year.