MOUNTAIN VIEW, Calif. -- The second floor of the Computer History Museum here was a sea of young entrepreneurs and top Silicon Valley investors going on speed-dates, and Qasar Younis was the matchmaker.

He surveyed the scene: hundreds of entrepreneurs, each with their own table, spread out across two giant rooms last week. Investors swarming around and plunking down for rapid-fire meetings that had been scheduled by algorithm the night before.

The low-key Younis is the chief operating officer of the start-up incubator Y Combinator, and he was presiding over that most vaunted of Silicon Valley rituals: the Y Combinator Demo Day.

Over the past 11 years, the incubator, which takes a 7 percent stake in the companies it invests in, has become one of the most important institutions in the region — hatching start-ups such as Dropbox, Reddit, Stripe and Airbnb with $120,000 in seed funding and matching them to investors. The three-month boot camp is also seen as bellwether for the valley's evolution — on diversity, on start-up trends, and lately, for how the tech industry views itself in relationship to the wider world.

This year's batch included the usual disparate gaggle of companies: Multiply Labs, a company 3-D printing dietary supplements, and Burrow, a start-up specializing in mail-order sofas for young professional millennials who move a lot and are sick of buying Ikea. There were a slew of drone start-ups — specializing in delivery, security, and surveying crops. A start-up trying to create credit scores for immigrants. Perhaps the most buzzy was Flex, a tampon alternative women can wear during sex.

Demo Day is actually a three-day event. During the first two days, roughly 100 fledgling start-ups stand on a stage and present two-minute pitches to a conference room of 500 investors, a model that has now been copied all over the world and helped inspire TV shows such as "Silicon Valley."

Like many things at Y Combinator, the third day is an experiment. Younis dubbed it Investor Day, which he described as “a more elegant and transparent” alternative to “the happenstance and informality” of typical fundraising. The traditional courtship process usually begins right after Demo Day, when start-ups begin canvassing venture capitalists' offices across the region in a frenzied hunt for cash. Y Combinator engineers had created special software that uses mathematical models to match investors with companies they might want to meet.

So here was Mamoon Hamid, a general partner at the venture firm Social Capital, fresh off a meeting with Validere, a start-up that was building a pocket-size sensor to test the quality of oil and gas. “The sales are amazing, the managers are amazing — that’s just a cash-producing business!” he gushed to Younis.

But, no, he wasn't opening his wallet. His fund focuses on bigger companies, he explained. Still, Investor Day was a great place to find inspiration, and he had other leads the event's software had chosen for him.

At the table for Flex, chief executive Lauren Schulte looked pleased. “We’re not taking in any new money,” she said, as she stuffed her device, which looks like a large female condom, into a plastic model of a woman’s genitalia. Flex was in an enviable position: It was only Demo Day, and they were already oversubscribed. The company would begin taking its first online orders that day.

Younis, wearing a gray hoodie and a T-shirt printed with the Y Combinator motto, "Make Something People Want," milled about one day last week, introducing his favorite companies. He was as enthusiastic about a building sensor that can identify burglaries as he was about a wristband that detects calories consumed by tracking blood flow. The 34-year-old, who grew up in rural Pakistan and sold his Y Combinator-backed messaging start-up to Google in 2011, spent hours talking with entrepreneurs, comparing strategies for taking a product to market, the merits of going public and ways to handle investors.

His iPhone was pinging every five seconds, with founders asking for gut checks and advice on how much to value their companies and how to read signals of interests from investors. “Game-time decision-making,” Younis explained. "For most founders, this is the first time they're raising money — a lot of the process is a mystery."

The room was full of notable venture capitalists backed by hundreds of millions of dollars, each hoping to find the next Airbnb. Underneath the event's friendly vibe was the status-consciousness that has led some to criticize the organization as elitist. Everyone watched which start-ups got the most meetings and money. Demo Days are invite-only; investors who are too aggressive with start-ups don’t get asked back.

“You’ve got all these investors here — it’s like, you're looking around, who is everyone talking to?” said Niko Bonatsos, managing director of the venture firm General Catalyst and a large investor in Snapchat.

“That’s good for the founders,” Younis shot back, grinning. The pressure he said, would stop investors from dillydallying, helping to create a "true marketplace."

"Everyone is looking for something above the hype," said Alex Gurevich of Javelin Venture Partners. “In truth, it’s impossible to tell. It's hard to get real-world intelligence from two minutes of pitching.”

In Silicon Valley, Y Combinator is often seen as bellwether. By its metrics, America's innovation hub is getting somewhat more diverse. Twenty-six percent of the companies in this season’s class, called a batch, had a female founder, compared with roughly 5 percent in 2008. Black and Latino founders were roughly 7 percent of the current class, but the group only began tracking underrepresented minorities last year.

There were also other shifts. Roughly a third of the companies were international — more than ever. The list included OMG Digital, a media company from Ghana that aims to be the “Condé Nast of Africa,” and Innov8, a company building co-working spaces in India. Roughly 5 percent of companies were focused on biotechnology and hard sciences, bucking the trend of copycat social networking and on-demand delivery apps that have flooded Silicon Valley in recent years.

Y Combinator was co-founded 11 years ago by entrepreneur Paul Graham, who held the first Demo Day in a rented house in Cambridge, Mass. The handful of investors who attended were mostly his friends. Y Combinator’s current president, Sam Altman, has extended the organization’s footprint far beyond technology.

He’s launched a nonprofit arm, called YC Research, which is funding an organization dedicated to promoting artificial intelligence for the good of humanity, a project to study and perhaps build a future city and a vast experiment in social welfare that involves giving monthly payments to poor people in Oakland, Calif. He's also planning to foray into online education, according to people familiar with the matter.

Younis has focused more on the organization itself. He has spent the past several years helping the incubator raise a $700 million “Continuity Fund,” which provides funding to later-stage companies. He has rebuilt and streamlined Y Combinator’s suite of software tools, which are built in-house and used for marketing, reviews and communication between entrepreneurs.

Younis's biggest concern is that the organization will become spread too thin. “Like all start-ups, we risk losing focus on core goals: servicing our founders and picking great companies,” he said. “It’s really about giving good advice — that’s the hardest thing to define, but it may be the most important thing. It’s easy to get distracted.”

In the days following the event, Younis was on the phone nonstop counseling entrepreneurs. Afterward, he used the organization's software to collect data on whether companies raised money on Investor Day. A handful of companies had. Others reported positive conversations.

Younis cautioned eager entrepreneurs not to get overexcited, because the process doesn't happen overnight.

"I tell them," he said, "unless you're exchanging signature blocks and wiring money, it's not a sign of anything."