E-Mail Before Millennials were over laugh-cry emojis, they were the most used emojis across the world, according to researchers at USC. The emoji was more popular than smiley faces say researchers who categorized millions of tweets across 30 countries and evaluated over 1700 emojis. Their study, "An empirical study of emoji usage on Twitter in linguistic and national contexts" was published in Online Social Networks and Media. Mayank Kejriwal, a research assistant professor in the Department of Industrial and Systems Engineering, and a research lead at the USC Information Sciences Institute who is the lead author on the paper, says approximately 100 emojis are used most often.