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.

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