Motion pictures had been around since the late 1880s, first as short reels and then, by the 1910s, as longer feature films.

With every year they grew in popularity, but any new technology usually takes a couple of decades to really get going.

And, in the 1920s, it took off.

Europe was devastated by WWI and film production essentially ceased.

That gave America a chance to catch up... and it did.

During the 1920s 90% of films being shown around the world came from Hollywood, where about 800 films were being produced every year - more than today.

The "Studio System" developed in the 1920s too, when American cinema was dominated by a small group of film studios which controlled all aspects of film production and distribution.

Many of the the names are familiar: Warner Bros, MGM, Paramount, Columbia, 20th Century Fox.

Films were already popular in the 1910s, but during the 1920s it truly became the form of mass entertainment.

And, to accomodate the huge audiences now attending every week, vast and lavish "movie palaces" were built. They say everything about the booming film industry.

It was also in the 1920s that the movie star was born; until then actors were rarely billed, as studios feared they might demand higher wages.

But in the 1920s they realised the huge appeal a familiar name could have, and actors were signed up to multi-million dollar contracts.

And many of the genres now familiar to audiences were fully established in the 1920s.

Crime dramas, romantic comedies, musicals, war films, and comedies - these latter being dominated by the titanic figures of Buster Keaton, Harold Lloyd, and Charlie Chaplin.

The historical epic was invented in the previous decade, but it was in the 1920s that it truly emerged.

Whether with Ernest Lubitsch's The Loves of Pharaoh, from 1922, which had a cast in the tens of thousands, or Cecil B. DeMille's The Ten Commandments, from 1923.

Somewhat surprising is that the 1920s were a golden age for horror - perhaps because silent movies and black-and-white are well suited to the genre.

Like The Terror, from 1928, which was the first all-talking horror. (Though critics did call it "dragging, fatiguing and boring.")

Or The Phantom of the Opera, from 1925.

It was an adaptation of the Gaston Leroux novel, which had been published only fifteen years earlier.

Since its beginning Hollywood has been no stranger to adaptations, sequels, prequels, remakes, and reboots.

Science fiction wouldn't properly develop for another few decades, but that didn't stop Fritz Lang from making Woman on the Moon in 1929.

There was also Aelita (1924) about a communist uprising on Mars, and The Mysterious Island (1929), an adaptation of the Jules Verne novel.

During the 1920s Hollywood was the home of commercial cinema.

In Europe, meanwhile, film was much more experimental. As in The Fall of the House of Usher, where director Jean Epstein tried out multiple exposures for a ghostly effect.

This was still a new technology and art form; there were no rules about how things should be done.

From Carl Theodor Dreyer's famous use of closeups in his psychological masterpiece, The Passion of Joan of Arc, to Abel Gance's Napoleon, which is six hours long.

All the way to Dziga Vertov's legendary 1929 documentary, Man with a Movie Camera.

He just wanted to explore the possibilities of the camera and see what it could do. Such was the spirit of filmmaking in the 1920s.

The most famous European cinematic style is German Expressionism, which borrowed plenty from the concurrent art movement.

It kicked off with The Cabinet of Dr Cagliari in 1920 and was continued by classics like Nosferatu in 1922 - a vivid, experimental cinematic language.

Prominent artists were also interested in cinema, whether Marcel Duchamp (of The Fountain fame) or Salvador Dali, who made a deeply avant-garde (and profoundly shocking) surrealist film with Luis Buñuel, called Un Chien Andalou.

Of course, the crowning achievement of 1920s European cinema (and perhaps of all cinema in that decade) was Fritz Lang's Metropolis, from 1927.

A budget-breaking visual spectacle and aesthetic miracle, with a cast of thousands and a set unlike anything seen before.

Soon enough America's booming cinema industry allowed them to attract with its riches the film stars of Europe.

Pola Negri was the first European actress to sign a contract with an American studio; she was followed by many more, including directors like Lubitsch and Murnau.

It was also a period of rapid technological and technical progress - new special effects were being invented all the time.

Like the Schüfftan Process, which used mirrors and allowed directors to create multi-part shots, projecting their actors onto models or miniatures.

But the greatest technological leap of the 1920s? Sound.

It started in 1926 with Don Juan, which included a partially synchronised soundtrack, but was most famously introduced with actual dialogue in 1927's The Jazz Singer.

And, from that moment, cinema changed forever.

The Motion Picture Academy was also founded in 1927, and the first Academy Awards presented in 1929.

It was, among other things, part of an attempt to clean up the reputation of Hollywood, which at that point was regarded as force of moral corruption.

One of the biggest early scandals was that of Fatty Arbuckle, a hugely popular comedian of the 1910s who signed a deal worth $1 million per year with Paramount in 1920.

Only a year later he was charged with the murder of a young actress during one of his famously wild parties.

And so, like many new industries, it was a while before regulation caught up with cinema.

The films of the 1920s were filled with violence, nudity, "immoral" themes, debauchery, nihilism, crime, religious satire, and much more.

Not all, of course, but more than you might think.

That all changed with the Hays Code, which was firmly established by 1934.

It banned everything from profanity to "excessive kissing" and nudity to sympathy for criminals.

The kind of thing freely depicted in the 1920s would not be seen again in movies for a long time.