Who: Charles, Prince of Wales, 72, and Diana (née Spencer), Princess of Wales, who passed away in 1997 at the age of 36.

How They Met: Prince Charles and Princess Diana first met in 1977 at a grouse-shooting event at the Spencer family home, Althorp. Charles was courting Diana's older sister Sarah at the time but took note of the younger Spencer. In the couple's engagement interview, Charles remembered Diana as "a very jolly and amusing and attractive 16-year-old."

Charles and Diana met again in 1980 when both were visiting Philip de Pass in Sussex. "When the [relationship] really started to get serious . . . I must have been 18 and a half," Diana recounted in footage from PBS special Diana: Her Story.

"I thought, 'I am quite impressed this time around,'" she said of her experience with the prince. But the royal came on, uh, strong, "like a bad rash." Diana said he was "all over me."

After a conversation in which the princess-to-be suggested Charles should have someone by his side, Diana said he "leapt upon me, started kissing me and everything." She recalled thinking, "'This is not what people do!'"

"He was all over me for the rest of the evening," she remembered. "Followed me around, everything. Puppy. I was flattered, but I was very puzzled."

By February of the following year, Charles and Diana were engaged. According to The New York Times, the prince proposed before Diana was set to leave for Australia.

"I wanted to give her a chance to think about it," he said, "to think if it was all going to be too awful."

Naturally, Diana accepted ("I never had any doubts about it."), but the honeymoon phase wasn't exactly in full swing. During the couple's engagement interview a reporter presumed that they were "in love," to which Diana agreed "of course," and Charles replied, "Whatever 'in love' means."

According to Diana herself, she and Charles had met only 13 times before they wed on July 29, 1981.

Though the wedding was globally decreed a "fairytale," appearances were reportedly deceiving.

Diana's former astrologist Penny Thornton recently revealed that the princess had told her Charles admitted "he didn't love her" the night before their wedding. "She thought about not attending the wedding," Thornton explained.

Diana told biographer Andrew Morton that she had second thoughts as well, telling her sisters, "I can't marry him, I can't do this, this is absolutely unbelievable." The response? "Your face is on the tea towels, so you're too late to chicken out."

Charles, too, reportedly reevaluated the marriage the night before, claiming, "I can't go through with it, I can't do it."

As we know, they went through with it. Diana later called her wedding day the "worst day of my life."

On their honeymoon, Diana spotted a new pair of cufflinks on Charles's wrists — a set of intertwined "C"s. They were a gift from Charles's ex-girlfriend, Camilla Parker-Bowles, which Diana identified as such immediately. When she called her husband out on it, Diana said Charles replied asking why that was wrong, adding, "They're a present from a friend."

Years later, designer Jayson Brundso, who worked with the princess in 1996, told Harper's Bazaar Australia that Diana objected to a pair of Chanel shoes he'd pulled for her to wear. "'No, I can't wear linked Cs, the double C,'" he recalled her telling him. "So I asked why, and she said, 'It's Camilla and Charles.'"

Why We Loved Them: Well … love (whatever that means … )? That's not quite the emotion we'd associate with Charles and Diana, but it is important to note that if it weren't for this relationship, Diana likely wouldn't have had the platform to accomplish the humanitarian good that she did. Also, we wouldn't have these royal qts!

When They Peaked: Early. In recordings used for Andrew Morton's 1992 biography Diana: Her True Story, Diana revealed that she and Charles "were very, very close to each other the six weeks before Harry was born," in 1984. "The closest we've ever, ever been and ever will be."

That changed the moment Prince Harry was born.

"As Harry was born, it just went bang, our marriage. The whole thing went down the drain," Diana said.

According to the princess, Charles wanted his second child to be a girl, and his disappointment following the birth was palpable. Diana remembered her husband saying, "Oh God, it's a boy," adding, "and he's even got red hair."

Interestingly, at the time of Harry's birth, Charles told reporters that his son's hair was an "indeterminate color" …

The Breakup: How much time do you have?

From the beginning, Charles and Diana's differences were glaring. The prince was known to make undermining comments about his wife's education level. In the early years of their marriage, royal biographer Tina Brown reported that during a solo trip to a friend's home Charles had commented on his European host's impressive English. When she replied that her father "believed in educating girls," Charles reportedly responded that he wished "that had been the philosophy in my wife's family."

Royal historian Sally Bedell Smith cited 1986 as the year in which Charles and Camilla began seeing each other again.

Diana had her suspicions about the affair, and in 1989 she confronted Camilla herself. "I know exactly what is going on," Diana recalled telling her husband's mistress. Camilla first feigned ignorance, but then replied, "You've got everything you ever wanted. All the men in the world fall in love with you. You've got two beautiful children. What more would you want?"

Her response? "I want my husband."

In 1992, tensions reached a breaking point when, first, Andrew Morton's biography (rumored to have been written in collaboration with Diana herself, a fact that has since been confirmed) was released. The book illustrated the princess's deep unhappiness in her marriage, noting the continuation of Charles and Camilla's affair, and revealing that Diana suffered from bulimia and had attempted suicide several times.

One particularly upsetting anecdote alleges that Diana had thrown herself down the stairs following an argument with Charles.

Then, two months later, The Sun printed the transcript of a phone call Diana had shared with a man named James Gilbey in 1989.

In said conversation, Gilbey repeatedly referred to Diana by the pet name "Squidgy" and professed his love for her. But despite the intensity and sheer volume of Gilbey's proclamations, Diana's replies are never gushing. "You are the nicest person," she says in response to his "I love you, love you, love you."

By Dec. 1992, Charles and Diana shocked the world by announcing their separation.

"This decision has been reached amicably and they will both continue to participate fully in the upbringing of their children,"Prime Minister John Major told the nation.

A statement from the palace assured the public that the Prince and Princess of Wales had "no plans to divorce" and that they would even occasionally "attend family occasions and national events together." The line of succession was also unchanged by this development.

Just weeks after the announcement was made, the royal family once again faced a recorded phone call scandal: Camillagate.

Another call from 1989, this one between Charles and Camilla, was released in January 1993 by the Mirror. Far more explicit than Diana's call with Gilbey, Charles's conversation will forever be known as "tampongate". "In the next life, I'd like to come back as your trousers," he told Camilla, calling her by his nickname for her, Gladys (she called him Fred). "I'd like to be where your Tampax is," he went on.

In a 1994 ITV interview with Jonathan Dimbleby, Charles admitted to being unfaithful to Diana during their marriage. When asked whether he tried to be "faithful and honorable," Charles said, "yes, absolutely," explaining that he was … "until it became irretrievably broken down, us both having tried."

The very night that the interview aired, Diana attended a gala in an off-the-shoulder little black dress now widely referred to as the princess's "revenge dress."

The following year, Diana sat down for her BBC Panorama interview with Martin Bashir. The controversial 1995 interview, which is thought to have damaged her relationship with the royal family beyond repair, confirmed much about Diana and her relationship with Charles.

Diana opened up about her eating disorder, calling her bulimia "a symptom of what was going on in my marriage."

"I was crying out for help, but giving the wrong signals," she went on, "and people were using my bulimia as a coat on a hanger: they decided that was the problem — Diana was unstable."

The princess also discussed Charles and Camilla's affair in the interview, describing the effect it had on her as, "Pretty devastating. Rampant bulimia, if you can have rampant bulimia, and just a feeling of being no good and being useless and hopeless and failed in every direction."

When asked whether she saw Parker-Bowles as a factor in the collapse of her marriage, Diana famously replied, "Well, there were three of us in this marriage, so it was a bit crowded."

Diana confirmed that the recording of her and Gilbey's conversation from 1989 was authentic, but clarified that "the implications of that conversation were that we'd had an adulterous relationship, which was not true."

She did, however, admit to her own affair with James Hewitt. "Yes, I adored him. Yes, I was in love with him," she said. Ultimately, though, the princess was "very let down" when Hewitt shared personal details about their relationship in what ended up being a somewhat salacious book.

Following the BBC interview, Queen Elizabeth wrote to her son and daughter-in-law, urging them to move forward with a divorce.

By July 1996, the divorce was finalized, and Diana was forced to give up her HRH title. The queen was reportedly willing to allow the princess to keep her title, but Charles felt strongly that it should be stripped.

Diana was upset by this development, but her son William reportedly comforted her. "Don't worry, Mummy," he said, "I will give it back to you one day, when I am king."

Years later, Tina Brown revealed details from a lunch she'd had with Diana shortly before the princess's untimely death.

"At the end of Diana's life, she and Charles were on the best terms they'd been for a very long time," Brown told The Telegraph. "Charles got into the habit of dropping in on her at Kensington Palace and they would have tea and a sort of rueful exchange. They even had some laughs together."

Though Brown said Diana had "accepted Camilla" and realized that she was "love of his life," that didn't change her feelings toward him. "She said to me at that lunch that she would go back to Charles in a heartbeat if he wanted her."

Where They Are Now: Charles and Camilla eventually married in 2005 and have been together ever since.

One year after her and Charles's divorce was finalized, Diana was in a tragic car accident while visiting Paris with her boyfriend Dodi Al Fayed. Diana, Al Fayed, and their driver Henri Paul were all killed in the crash.

#TBT: Check in every Thursday as we throw it back to some of our favorite celebrity couples of all time.