Twitter, the quirky 140 character messaging service that’s become a global phenomenon, priced its initial public offering at $26 per share, valuing the seven-year-old company at over $18 billion.

Twitter (TWTR) will raise $1.8 billion to fund future expansion by selling 70 million shares, which will open for trading on Thursday morning on the New York Stock Exchange. Some analysts say the shares are worth $50 or more, so the price could explode higher once trading begins.

Started in 2006 as a simple way to share short messages and status updates among friends, Twitter has grown to 232 million active users who post 500 million tweets per day about everything from personal thoughts to celebrity gossip and breaking news.

The deal is the highest profile Internet IPO since Facebook (FB) raised $16 billion last May. And Twitter could rank as the second-largest debut of a U.S. Internet company in history if it ultimately surpasses the $1.92 billion raised by Google (GOOG) in its 2004 IPO, according to Dealogic. Underwriters of the Twitter deal have the option to sell up to another 10.5 million shares, if needed, under a standard IPO clause called the greenshoe option, pushing the total value to over $2 billion.

Twitter and its Wall Street underwriters led by Goldman Sachs (GS) are hoping the deal goes smoother than Facebook’s IPO last year. Facebook shares faced delayed trading due to technical glitches, then couldn’t hold above the IPO price of $38 due to oversupply and doubts about the company’s mobile strategy.

Twitter goes public as a much smaller company. It brought in just $534 million of revenue for the 12 months ended September 30 leading to a net loss of $137 million. Facebook had revenue of $3.7 billion and $1 billion of profit when it went public.

Helping increase interest in Twitter, the company chose to sell shares at a time when related social media stocks have been booming. Facebook is up 85% so far this year and LinkedIn (LNKD) is up 92%. Even Groupon (GRPN), the troubled coupon sharing service that lost three-quarters of its value last year, has doubled in 2013.

Still, some investors worry that Twitter’s growth is stalling out and that it won’t be able to bring in as much money running advertisements as its more popular big brother, Facebook. Twitter’s active user base increased by 25% in the first nine months of the years compared to a 43% jump in the same period last year. Analysts say Twitter will have about 700 million shares outstanding on a fully diluted basis after the IPO.

There’s no question about the increasing importance of Twitter as a global communications platform, however.

Demonstrators in the Arab Spring uprising used Twitter to coordinate and publicize their efforts. The first reports of US Air flight 1549 making a safe water landing on the Hudson River came from an eye witness’s Twitter account. And President Barack Obama celebrated his reelection victory last year by tweeting a picture of himself hugging his wife below the words “Four more years.”

Twitter began the formal process to go public by filing with the Securities and Exchange Commission in July. But using a provision in the new JOBS Act, Twitter kept its filings secret until disclosing the preparations in a tweet – how else -- on September 12. The actual filings detailing Twitter’s financial condition wasn’t made public until the beginning of October.

The deal makes Twitter co-founder and former CEO Evan Williams a billionaire, at least on paper. Williams owns 56.9 million shares of Twitter, worth $1.5 billion at the IPO price. Jack Dorsey, another co-founder, owns 23.5 million shares worth over $600 million.