Twitter is being added to the S 500.
Shares of the social network hit a three-year high after the news was announced.
Follow Twitter's stock price in real-time here.
Shares of Twitter gained more than 4% in early trading Tuesday after S Global announced the social-media company will replace Monsanto in the S 500 index.
Monsanto's merger with Bayer was approved by the US Justice Department last week.
Twitter’s overnight gains continue a red-hot streak that began with the social network’s strong first-quarter earnings report in April.