Batman and Superman are two of DC Comics’ most popular superheroes. As members of the Justice League, they’ve formed a strong sense of respect and friendship with each other. The two heroes will finally appear on the big screen together in Batman v Superman: Dawn of Justice, but they won’t be getting along too well. Here’s 7 things you should know before seeing the film.

The idea of Superman and Batman appearing on the big screen was teased back in 2007’s I Am Legend. In the movie, Will Smith is a survivor of in an post-apocalyptic New York City. A giant billboard can be seen with a Batman vs. Superman logo and the date: 5-15-10. Warner Bros. attempted to make the movie in 2002 in order to revive the Superman franchise. Instead, the studio went with 2006’s Superman Returns.

The first time to two met in a full length comic was 1952’s Superman#76.

Both Clark Kent and Bruce Wayne have decided (separately) to take vacation and go on a cruise. The ship was overcrowded so the two had to share a room. This was a concern for both since they each had a secret to maintain.

When a robbery and fire take place near the dock, Bruce suggests turning off the lights so he can turn in. In the dark, they both figure they can change into their superhero identities. Unfortunately, the light from the flames outside lights up the room and they both discover each other’s secret.

There have been other versions of their first meeting over the years. In the movie, we know that during Superman’s fight with Zod, a Wayne Financial building was destroyed, killing hundreds inside. The threat of Superman’s power is what makes Batman decide to take on Superman.

Even though they’ve become great friends in the comics, the two have fought many many times. The most notable fight was in 1986’s The Dark Knight Returns. This story, set 20 years into the future, showed the ultimate showdown between the former allies when the world changed and heroes took a different stance on fighting evil.

Another time was when Poison Ivy took control of Superman and commands him to fight Batman. Batman uses a Kryptonite ring and other weapons against him.

The two have also fought in the animated Batman Superman Movie in 1997 and numerous other comics.

Despite the having a movie center on two heroes fighting, Batman and Superman have actually formed a strong friendship in the comics. The Kryptonite ring Batman used against Superman originally belonged to Lex Luthor. Superman entrusted it with Batman, to be used if he ever went out of control and needed to be stopped.

Wonder Woman first appeared in 1941’s All-Star Comics #8 with her origin fleshed out more in 1942’s Wonder Woman #1. Wonder Woman comes from Themyscira, an island of Amazons. Originally her mother made her out of clay. She then came to life and had incredible abilities.

It was recently revealed the story of her being made from clay was a cover. Wonder Woman was actually the daughter of Zeus and the story was created to prevent Zeus’ wife Hera from murdering Wonder Woman out of jealousy. Wonder Woman is a demigod and, in the movie, is thousands of years old.

Doomsday was created on Krypton in ancient times. Scientists sent a baby to face the viscous creatures outside. The remains were cloned and the process was repeated over and over.

After over thirty years, the baby evolved and no longer needed to breathe or eat. He turned on his creators and escaped the planet. Eventually he was captured and contained. He would make his way to Earth and battle Superman, which resulted in both their deaths. Of course, Superman eventually returned after his death.

In the movie, Lex Luthor obtains Zod’s body and does some experiments of his own. This is likely how Doomsday is introduced into the movie.

Batman and Superman will have to put aside their differences and team up with Wonder Woman to defeat Doomsday.

Lex first appeared in comics in 1940’s Superman #4. He originally had hair and was simply referred to as “Luthor.”

Lex Luthor is played by Jesse Eisenberg. He’s mainly been seen with hair, but he will go bald during the movie. A recent Lego set showed both versions of Lex. Eisenberg also told the LA Times, “When you see the movie, you’ll see. It’s the greatest scene that I’ve ever gotten to take part in—it accounts for the change in hair.”

Another thing you can expect in Batman v Superman: Dawn of Justice is plenty of action. The movie smashes its way into theaters on March 25. This movie marks the beginning of a bigger cinematic universe for the DC Comics character and we’re in for a big treat.