Marketers who have yet to get serious on Snapchat may want to consider doing so, and soon. The ephemeral messaging platform is experiencing a surge in growth, with its monthly user base expected to grow by double digits this year and wind up topping not only Twitter but Pinterest, according to a new report by eMarketer.

Bloomberg reported last week that Snapchat had reached 150 million daily users, surpassing Twitter's 140 million daily users. Now eMarketer is saying that Snapchat's U.S. monthly user base will grow 27.2% this year to 58.6 million users, a growth rate eMarketer said exceeds that of messaging apps in the U.S., which will grow about 16%.

Twitter will have 56.8 million monthly users in the U.S. this year, the report said, and Pinterest will have 54.6 million users. Between this year and 2020, Snapchat will add 26.9 million users, nearly double that of Twitter and Pinterest, eMarketer said.

Despite its explosive growth, Snapchat has a ways to go to rival Facebook Messenger, by far the dominant messaging app in the U.S. Facebook Messenger will have about 105.2 million users in the U.S. in 2016, nearly twice Snapchat's user count. EMarketer pointed out in the report that nearly two-thirds of the U.S. population will use Facebook Messenger at least once a month in 2016. Facebook Messenger has grown significantly this year alone. In January 2016 it announced it had 800 million monthly users overall; in April, it said it had reached 900 million.

The eMarketer report also said that the gap between Messenger and its rival will continue to grow. In 2016, Messenger will boast 46.6 million more users than Snapchat, according to eMarketer. But by 2018, it will have 53.7 million more users.

Snapchat will also have to continue to build its capabilities to demonstrate results to its advertisers.

But marketers are eager to reach the particular users on Snapchat, who tend to be younger. Its website says that more than 60% of 13-to-34 year olds in the U.S. are Snapchatters. It also said that the platform has more than 10 billion video views daily.

EMarketer's report said that "Snapchat's biggest user base is between 18 and 24, with that age range representing 34.0% of Snapchat's user base this year. That's followed by Americans between 25 and 34, which represent 27.0% of Snapchat's US user base. The fastest growing US age group for Snapchat is people under 12, which will grow 42.9% this year."