“It’s been a long life,” Giancarlo Giammetti tells The Daily Beast.

Indeed it has. Giammetti, now 75, has always been a sort-of fashion insider. Best known as fashion designer Valentino Garavani’s longtime partner (although he claims the two have not been romantically involved since the Seventies), Giammetti is both a business and social force to be reckoned with. The duo’s relationship dates back to the Sixties—July 31, 1960, to be exact—when a friend of 28-year-old Valentino approached 22-year-old Giammetti at Parisian nightclub Pipistello. “I’m here with a couple of friends. Could we join you, since there are no other seats available?” He asked Giammetti. That was the night he was introduced to Valentino—and, well, the rest is history.

Born and raised in a changing Rome, Giammetti watched his hometown transform from World War II Nazi occupation to la dolce vita to the global force it’s known as today. Hailing from a “bourgeois” family, as he describes, with parents who wanted him to become an architect, Giammetti never imagined a career in the fashion industry. But he dropped out of architecture school and instead took a chance on Valentino’s budding design house. Choice well made. Valentino helmed the creative end, while Giammetti took care of business. Together, they were—and still are—an unstoppable duo.

“I think that there was—or is—a real closeness of Valentino and mine that never stopped,” Giammetti says. “Fundamentally, it boils down to so much love and respect and support. We are the best of friends; we are brothers; whatever label you wish. We both wanted to succeed; we both were ambitious, curious, and fascinated by the world that was in front of us. It was a path that we couldn’t direct. It was normal. It was life that brought us there.”

Giammetti bought his first camera at 25. “It’s very strange. When I first started taking pictures, I was doing Polaroids,” he said. “Polaroids were really about sharing. I remember dinners with Andy Warhol or people, especially in Europe, who were using them. [They] were there on the table for everybody to share, to steal, and to comment.” He carried it everywhere, snapping photos of nearly everything and everyone he encountered. By the time he decided to compile the images for his new book, Private: Giancarlo Giammetti (Assouline, $250), out Friday — he had amassed over 57,000 photos.

Offering a lens into his travels, his friendships, and his work, Giammetti’s book is, as he describes it, for sharing. He opens up, offering for the first time a look into his and Valentino’s very private lives.

He talks about his friends—“The Tribe,” as he calls them. “Something that makes me very happy,” Giammetti writes, “is that our tribe has never stopped growing; we always have new energy around us… Valentino and I never lost that youthful instinct to make new friends.” He cites friends-turned-colleagues who have been with them since the beginning—Daniela Giardina and Georgina Brandolini—close celebrity friends such as Gwyneth Paltrow, Madonna, Anne Hathaway, and Elizabeth Taylor, and industry supporters including Anna Wintour and Diana Vreeland.

“This is a world where you’re always trying to meet people,” he says. “And [Vreeland] was an amazing inspiration for all of us. Not just because she knew about fashion, or because she worked at Vogue, but because she was Diana Vreeland. She would talk about the last show on Broadway—she took us to see Hair, which at the time was like going to the most outrageous place. She went to see Hair a thousand times,” he laughs.

Vreeland would have amazing dinner parties too, Giammetti says. “One night [Vreeland] said ‘I want to have a dinner for you guys, who would you like to meet?’ I think we were 25 or 26, so really, [we were] very young. We knew that Sophia Loren was in New York at the time, so, we said ‘The biggest Italian superstar is here, do you know her?’ And she said “Of course, I know her. I will ask her to come.’”

He explains that Loren had been robbed of all the jewelry from her New York home on Central Park West, so naturally she was refusing to leave her home to avoid the paparazzi.

“We were a bit disappointed, but we went to Diana’s house anyway because it was never something boring,” he continues. “And Diana said ‘Oh, I have another surprise for you.’ And out from a room comes Barbra Streisand.”

But when I ask if he was starstruck by all of the celebrities he has met, all of these people he now calls friends, Giammetti insists that deep down, they’re all the same people; they’re all just human. “You choose friends—whether they are an actor or a drugstore owner—because you like them as a friend, not because of what they do. I think it’s beautiful that I can have a relationship [with my friends] and not talk about their movie business or how many covers of Vanity Fair they’ve had. I like to talk about their lives, their doubts, their joys, their children, food, or whatever else. So, I try to choose them not by their style, but by their real human being, and what I want to see in my friends.”

And luckily, through all of the friendships and the memories, Giammetti’s camera was around to capture all of the magic.

Giammetti—who laughs when I tell him he’s big on Instagram—has racked up over 34,000 followers on the photo-sharing platform. “Even today I took pictures of me and Valentino having lunch and put it on Instagram, it was an hour ago,” he said. “Now, Facebook, especially Instagram, has again made it possible to share your moments with somebody else. There is a connection between then and today.”

So much has changed since the “then” and the “now” in his life—Rome, photography, relationships. Yet, the fashion house that Valentino and Giammetti built still remains a fashion force to be reckoned with.

“Valentino is one of the few designers that really created his own style,” Giammetti says. “He created the DNA of the house, and I created a certain glamour, a certain lifestyle that goes with the name. The designers today [Maria Grazia Chiuri and Pierpaolo Piccioli] were with Valentino for ten years—so, they learned that DNA. They try to express their vision of Valentino but with the same attributes—beauty, romance, femininity, and fragility. These are the things that a designer has to understand, that they cannot just create and follow every season. They have to create their own style, like Chanel with [Karl] Lagerfeld, [Giorgio] Armani, [Gianni and Donatella] Versace, and Oscar de la Renta. [Their style] is an evolution of one idea and that’s how they will survive. That’s how a house can survive forever.”