Scholars debate whether kissing began as a trend that spread around the globe, or sprung up organically in different regions. Whatever the case, the earliest known written mentions of it are in Vedic Sanskrit scriptures circa 1500 B.C., according to research by Vaughn Bryant, an anthropology professor at Texas A&M University. These scriptures, known as the Vedas, were foundational to the religion of Hinduism.

After that, kissing continued to appear in ancient Indian and Hindu literature. The Mahabharata, a Sanskrit epic compiled by the 4th century A.D., has a line in which someone “set her mouth to my mouth and made a noise that produced pleasure in me.” The Kama Sutra, an ancient Sanskrit text on eroticism and love, also has a chapter on kissing that identifies different methods of kissing and types of kisses.

Kissing isn’t just a romantic act. It can also be a sign of friendship or betrayal. In the Gospels of Matthew and Mark, written circa the 1st century, Judas betrays Jesus by identifying him with a kiss so that armed men can take him away and eventually kill him.

Judas’ kiss has since become a popular storytelling allusion. It may have inspired the “kiss of death” that appears in mafia literature and film (but was probably never an actual mafia practice). Perhaps the most famous example is in The Godfather Part II, when Al Pacino’s character gives his brother Fredo the kiss of death for betraying him.

The first people to smooch on film were May Irwin and John C. Rice, who appeared in a short film known variously as May Irwin kiss, Kiss or The Kiss. In 1896, the two performers went to Thomas Edison’s studio in New Jersey and reenacted their final kiss scene from a play they were putting on in New York City.

On stage, no one thought the kiss was that sensational. But many felt the close-up footage of them kissing was too risqué.

Video courtesy of USC School of Cinematic Arts, Hugh M. Hefner Moving Image Archive

In 1898, black performers Saint Suttle and Gertie Brown starred in a short film titled Something Good-Negro Kiss, the first film to show Black Americans kissing. In 2017, film historians rediscovered the footage, which was filmed by a white man named William Selig in Chicago.

“There’s a performance there because they’re dancing with one another, but their kissing has an unmistakable sense of naturalness, pleasure and amusement as well,” Allyson Nadia Field, a professor of cinema and media studies at the University of Chicago who helped identify the film, said in a university press release. “It is really striking to me, as a historian who works on race and cinema, to think that this kind of artifact could have existed in 1898.”

On the morning of August 14, 1945, patients burst into Greta Zimmer’s Manhattan office claiming the war in Japan was over. The Austrian immigrant wasn’t sure what to think, so on her lunch break, she went to Times Square in her white dental assistant’s uniform to see what the news ticker said. The atmosphere there was celebratory, and the ticker confirmed that it was indeed V-J Day, and World War II was over.

As Zimmer looked away from the ticker, a Navy sailor named George Mendonsa—who’d started drinking early and mistook Zimmer for a nurse—ran up and aggressively kissed her, leaving his girlfriend behind. Zimmer struggled to push the stranger off, and they parted ways. But unbeknownst to both of them, photographers Alfred Eisenstaedt and Victor Jorgensen had each captured the moment, as recounted in The Kissing Sailor: The Mystery Behind the Photo that Ended World War II.

Eisenstaedt’s photo became one of the most iconic WWII images in U.S. history, in part because viewers mistook it for a picture of a Naval officer and nurse celebrating together. The photo has also stirred controversy, as many people have claimed over the years to be the couple in the image, while others point out that it depicts a nonconsensual moment.

Zimmer, herself, said in an interview with the Library of Congress in 2005, “It wasn’t my choice to be kissed...the guy just came over and kissed or grabbed!”

When William Shatner and Nichelle Nichols kissed on a 1968 episode of Star Trek, it was not technically the first interracial kiss on U.S. television. But it was the one that seemed to have the most cultural impact.

In the episode, titled “Plato’s Stepchildren,” Captain James Kirk and Officer Nyota Uhura encounter aliens who force them to kiss each other through telekinesis. In Nichols’ book Beyond Uhura: Star Trek and Other Memories, she recalls that NBC was worried how white Americans would react to the scene, so they asked the actors to film two scenes: one with a kiss and one without a kiss. However, Nichols and Shatner purposefully messed up all of the kissless takes in order to ensure that NBC aired the kissing scene.

During the Cold War, leaders of communist states often greeted each other with what’s called the “socialist fraternal kiss.” This could be on the cheek or the mouth, but the most famous example is French photographer Régis Bossu’s 1979 picture of the Soviet Union’s Leonid Brezhnev and East Germany’s Erich Honecker kissing on the mouth.

The kiss occurred when Brezhnev visited East Berlin to celebrate the 30th anniversary of the German Democratic Republic (i.e., East Germany). When the Berlin Wall came down in 1989, the Soviet artist Dmitri Vrubel recreated the image in a mural on the wall’s east side. He captioned it: “My God, Help Me to Survive This Deadly Love.”