History reports that, in 1932, the now-famous Mars confectionery company was in some trouble. Forrest Mars Sr. moved to the U.K. as his relationship with his father (and partner in the company) eroded. There, he discovered, while creating his now-also-famous Mars bar for fighters in the Spanish Civil War, that some customers were eating Smarties (per ThoughtCo): iconic candies consisting of chocolate in a crunchy shell. This, History goes on, resolved an issue that had been troubling the industry at the time: chocolate was unpopular when the weather became hotter because it melts at the drop of a hat.

ThoughtCo adds that Mars partnered with Bruce Murrie and M&Ms (named after the two mens’ surnames) were patented in 1941. Soon after, the United States joined the Allies in World War II and, per History, they became a crucial part of the troops’ diet. M&Ms do indeed melt in the mouth rather than in the hands, and sometimes fans just don’t appreciate what a big deal that could be.

The candy became a smash so quickly that, according to M&Ms, the ‘m’ brand started to be added at the turn of the 1950s so that customers would know they were getting the genuine article, rather than another company’s version. “Look for the m on every piece” was the slogan.