For Star Wars fans, May 4 is a day to celebrate. The famous line — "May the force be with you" — was first heard when the movie was screened in 1977. It didn't take long for the Star Wars community to make a pun out of it. And so, May 4 came to be known as Star Wars day — "May the 4th be with you."

On May 25, 1977, the first Star Wars film was shown in cinemas. In the US, "Star Wars" was sold out for weeks. Hoping to snag a seat, audiences diligently lined up outside cinemas as shown here in Los Angeles. At that time, no one could have expected the series to span decades.

Obi Wan Kenobi utters this famous line to Luke Skywalker just before he is sent on a difficult mission. With the help of the "force," Luke is able to fight the empire on behalf of the Rebel Alliance. The empire has been threatening the entire galaxy with its planet-destroying Death Star space station. Forty years ago, audiences first heard the Jedi leader utter this unforgettable sentence.

Jedi master Yoda teaches Luke Skywalker how to harness the power of the "force." Using spiritual strength, it allows jedis to move objects with their minds. Yoda also trained Luke's father Anakin. Yoda sent him on his way with these wise words: "Fear is the path to the dark side. Fear leads to anger. Anger leads to hate. Hate leads to suffering."

Anakin ignored the wisdom of Yoda and allowed himself to be seduced by the dark side of the force. He became Darth Vader, the vicious right hand of the even more evil emperor. In "Star Wars - Return of the Jedi," Darth Vader fights Luke Skywalker and shocks him by saying: "Luke, I am your father."

He is the one responsible for manipulating young Anakin Skywalker and convincing him to join the dark side. "I can feel your anger. It makes you stronger," he says after killing a Jedi before Anakin's eyes. "Become my apprentice. Learn to use the dark side of the force." The emperor also assures him he will be a good Sith lord and gives him the name Darth Vader.

Golden C3PO and navigation droid R2D2 are the legendary robot pair featured in the Star Wars saga. Together, they sometimes resemble an old married couple, mainly due to C3PO, who takes every chance he can get to cheekily scold the smaller droid. "You'll be malfunctioning within a day, you nearsighted scrap pile," he tells R2D2.

This is what Luke Skywalker said about his twin sister Leia long before he knew that they were related. The droid R2D2 brought Obi Wan Kenobi a plea for help from Leia in the form of a hologram. "Help me Obi Wan, you're my only hope," she famously says. Luke is fascinated, and accompanies Obi Wan to Alderaan, Leia's home planet.

Star Wars fans have known for 40 years that the episode dates cause narrative confusion. After Episodes IV to VI were released between 1977 and 1983, George Lucas told the back-story in episodes I to III, which premiered between 1999 and 2005. The latest film "Rogue One" (2016), takes place between episodes III and IV.

George Lucas left the saga in the hands of Disney. The new series has won over new fans and places Episode VII (2015) in a familiar setting. Thirty years have passed since the rebels' victory over the empire and while new villains have appeared, so has Rey — a new heroine. It is assumed that she is the daughter of a Jedi knight, since she feels the force.

The latest film tells the story of a young Han Solo. Actor Alen Ehrenreich plays the renegade space pilot with humor and respect for the original character, portrayed by Harrison Ford. Taking place before Episode IV, the film explains how Solo got to know his Wookie pal Chewbacca.

In 1977, the smuggler Han Solo, Princess Leia and Luke Skywalker appeared for the first time on the silver screen. The trio was central to episodes IV-VI, (Star Wars, 1977; The Empire Strikes Back, 1980; Return of the Jedi, 1983), and met again decades later in Episode VII - The Force Awakens, from 2015.

Since 1977, Star Wars enthusiasts have been regularly celebrating the release of a new episode. They don't mind the jumps in the timeline. A real Star Wars fan knows exactly "when" each episode is set. The events in Rogue One take place between Episode III - Revenge of the Sith and Episode IV - A New Hope, the new title for the original Star Wars movie.

In the Star Wars universe, members of the Jedi Order use their power to do good. The Force gives them superhuman abilities. For example, they can move objects using their mind. Their strongest weapon is the lightsaber. The most famous Jedi Knights are Luke and Anakin Skywalker (the latter is shown right in the picture), Obi-Wan Kenobi (left) and Master Yoda.

Yoda is the most powerful Jedi Knight of all time; he knows how to use the Force like no other. For over 800 years, he has been training young disciples, known as Padawan learners, to become Jedi Knights. His language is strange; his words are wise. He is only 66 cm (26 inches) tall, but even his largest opponents know the Jedi Master should not be judged by his size.

In Episode V - The Empire Strikes Back, Yoda trains the young Luke Skywalker. Luke is very insecure and does not believe in his powers. Yoda teaches him the Jedi philosophy and new mental skills. He also warns him not to let negative feelings take over: "Anger, fear, aggression. The dark side are they. Once you start down the dark path, forever will it dominate your destiny."

The Sith are an Order on the dark side of the Force. Sith are mostly former Jedi Knights who have left the light side hoping to obtain more power. Famous Siths include Darth Vader, Darth Maul and Darth Sidious. Pictured here is Darth Tyranus, who was known as Count Dooku when he was a Jedi.

Darth Vader used to be Jedi Anakin Skywalker. Wanting to save the life of his wife and unborn children, he was pulled into the dark force by the Galactic Emperor himself. Anakin then became Darth Vader, while his children Luke and Leia were rescued and hidden. Twenty years later, Luke and Vader met again in a climatic confrontation, where the son discovered that the grim figure was his father.

He is actually a charismatic member of the Senate governing a large planetary republic. But secretly, Sheev Palpatine is a Sith Lord named Darth Sidious. He calls for an uprising against the Republic. He rises to the position of Supreme Chancellor and then Emperor, aiming to rule on the entire universe. He is responsible for the worst of all weapons...

The Death Star is the Imperial super-weapon. It's the size of the moon and is devastatingly destructive. Princess Leia witnessed a cruel demonstration of its power, as a blast from its superlaser destroyed her home planet, Alderaan. The Death Star had a weak point, allowing the rebels to strike back and destroy it — but the next Death Star was already under construction.

Controlled by the dark side of the Force, hundreds of thousands of soldiers — the stormtroopers — are the main ground force of the Galactic Empire. They have always been loyal to the supreme commander, the Galactic Emperor, and follow their superiors — such as here, Kylo Ren — without questioning them. In Episode VII, stormtrooper Finn breaks with this tradition and joins the good guys.

Along with humanoids, the Star Wars universe features a few inhuman creatures, such as the powerful criminal Jabba the Hutt, a disgusting monster who has unfinished business with the ex-smuggler Han Solo. In order to reinforce his demands, he enslaves Princess Leia. The bikini worn by actress Carrie Fischer in that scene has become legendary.

The Imperial weapons' massive size alone is already meant to frighten opponents. The four-legged AT-AT walkers are combat vehicles that can move quickly on any terrain while transporting troops. Their heads contain tons of the destructive projectiles. A similarly evil combat device is the two-legged All Terrain Scout Transport, or AT-ST.

While the Death Star was still being built, the ships of the Imperial fleet were holding the fort. Pictured here is a gigantic Star Destroyer, flanked by small and maneuverable starfighters that combat the Rebels in their own rapid ships, leading to fast-paced duels. In 1977, Star Wars creator George Lucas established new standards in special effects with these spectacular scenes.

Composer John Williams wrote the soundtrack to all Star Wars films. The main theme and the dark march accompanying Darth Vader are world famous. The song "Cantina Song" from Episode IV also became instantly cult. It is played by the alien band Figrin D'an and the Modal Nodes in the original 1977 film.

Smuggling belongs to Han Solo's past by Episode VII, and his relation with Princess Leia is also over — even though they are married. After many years, they meet again, and once again, their goal is to fight against the Empire. They're all older — except Han Solo's loyal friend, the Wookie Chewbacca, who accompanies Han until the end. His growl is legendary.

Already present in the first films, the golden know-it-all droid C3PO and his small beeping counterpart, R2D2, make up one of the most iconic twosome of film history. In Episode VII, another cute robot joined them: BB-8 (left). These three droids are loyal to the main characters and have already saved them from perilous situations.

Introduced in Episode VII, Rey is a new heroine whose origin still hasn't been explained. Is she the daughter of Leia and Han Solo? Or Luke Skywalker's? No one knows what happened in the 30 years after Episode VI - Return of the Jedi. Rogue One invited audiences to go back in time to find out.

This stand-alone spin-off movie is set in the period between Episode III and IV. The Empire is building its first Death Star and wants to test its destructive power. As Star Wars fans know, it can destroy a whole planet with a single blast. The Rebels want to steal the design plans for the weapon. The whole story runs parallel to the original Star Wars narrative.

Just before Christmas 2017, the eighth part of the Star Wars saga was released. In Episode VIII - The Last Jedi, Rey tries to win over Jedi recluse Luke Skywalker and bring him back into the Resistance. Meanwhile, the "First Order" wants to completely annihilate the rebel army led by Leia Organa. Poe and Finn do their best to prevent this.