When you walk into Facebook's Menlo Park, California, offices, the posters bombard you: "Let's Kick the Shit Out of Option B." It has the ring of a corporate mantra, à la "Move fast and break things," Mark Zuckerberg's famous exhortation to his colleagues. But it's something far more personal--a quote used by Facebook's second-in-command, Sheryl Sandberg. Already one of the most admired executives in America, thanks to Lean In, her 2013 female-ambition manifesto, Sandberg became a different kind of symbol in May after the sudden death of her husband, SurveyMonkey CEO Dave Goldberg. Facebook's COO had often credited her professional success, in part, to her supportive partnership with Goldberg. Together they were the model Silicon Valley power couple. It turns out Sandberg's "Option B" line is from a raw, public Facebook post she wrote a month after her husband died, about coping with grief after the loss of "Option A," the life she had expected to share with Goldberg. The post has been shared almost 400,000 times.

On a steamy August afternoon, Sandberg is dealing with the tragedy the best way she knows how--by throwing herself back into her work. She's in a conference room at the center of Facebook's new 430,000- square-foot Building 20. Like her boss, Sandberg has an open-plan desk. But it's clear by the pool of personal effects at the head of this conference table--lip balm, hand weights, a jumbo Diet Coke, and a rubber physical-therapy rod that she uses to treat the wrist pain she developed while writing Lean In hunt-and-peck style--that this is where Sandberg spends most of her days in back-to-back meetings. She'd like to learn to type, she says, but who has the time? After Goldberg's death, she took on yet another commitment by joining the board of SurveyMonkey. If the rumor mill had its way, she'd be busier still; she's always being touted as a candidate for some political office or CEO gig.

To her, it's just noise, though. What preoccupies Sandberg these days is small business. Having proved that the social network could move the needle for big marketers--like General Motors, which publicly dissed Facebook as an advertising medium in 2012, only to come slinking back a year later--Sandberg is now leading a campaign to convince companies of every size that it can do the same for them through a combination of simple content-creation tools and sophisticated ad-targeting. The message is getting through. More than 45 million small businesses have active Facebook pages. Two million of them are current advertisers, and more than a million have experimented with video advertising. Facebook hopes still more will sign up to use new tools it added in September, including customizable pages and inbox management.

In a candid conversation with Inc., Sandberg reveals that her passion for entrepreneurs is rooted in her ancestors, argues that Facebook will become the amplifier for small businesses, and explains that men still aren't comfortable with women in power.

Inc.: Let's talk small business.

Sandberg: This is literally my favorite topic, and I don't get to talk about it as much as I want.

Why is it your favorite topic?

Small business, medium business, SMB--there are 20 different names for it--but this is the source of economic growth. It really is. If you look at the job creation numbers in the United States, you look at them in Europe, the majority of job creation happens through small business. And people don't fully understand that or appreciate it in a world where economic growth is so important and job growth is so important. Just personally, my family immigrated here. My grandfather had a paint store. It's what put my mom through college. Small business is part of my family history.

What do small businesses have to do with your core mission of making the world more connected?

We give a voice to people who otherwise don't have one. Before social media, if I as an individual wanted to publish something to the world, unless I could get some local TV crew to interview me or I wrote an op-ed or took out an ad, I had no voice.

"My grandfather had a paint store. It's what put my mom through college. Small business is part of my family history."Sheryl Sandberg

Big businesses have always had a lot more voice. They can afford advertising, they can afford marketing. But for small businesses, being able to quickly and cheaply connect to customers is a big deal. Thirty-five percent of small businesses don't have a website. That's because they are expensive and hard to do and not obvious. Small businesses are typically run by one person, the owner, who has few resources, no time. But a Facebook page is easy and fast and gives you a webpage not just on desktop but, more important, on mobile. It's free, and it takes three minutes.

A lot of businesses have accused Facebook of suppressing the organic reach of their page posts to encourage them to buy advertising. To some extent, the messaging you've been doing around small businesses is about making them feel like Facebook cares about them, right?

We've cared all along, but we're maybe showing that care better now. I think the best way to show you care is to make the products efficient.

One in five minutes spent in mobile apps is on Facebook. Facebook pages are, as you said, replacing websites for some businesses. Customers can buy items there, book tables there, chat with customer service. Is the vision to capture all the activity that now happens on the internet and bring it inside Facebook's walls?

The goal is to provide as much value as possible. How do we help you grow your business? If we are growing the top line for businesses and helping them achieve their goals, they'll continue to do more and more with us.

What kind of success has the Lean In movement generated?

We have 24,000 circles in 117 countries. We were hoping for a thousand. We grow by a hundred a week. They're growing because they help people accomplish real things. Our data says the great majority of people who join a circle will make a really positive life change for themselves within six months. They get raises. They get new jobs. They run for office. They change the dynamics they have with their partners. Some of them drop their boyfriends and decide they want new boyfriends who will be more equal partners.

Over and over, the circles actually give people strength. The thing about women is you really get a lot of messages of "Why?"--"Are you sure you want that job? Don't you want kids one day?" I always ask an audience: "If you're a man, please raise your hand if anyone's ever said, 'Should you be working?'" Never had a hand. Do you know how many times women are asked if they should be working? There's this assumption that women can't work and have families, which is a really unfair assumption given that almost 70 percent of mothers have to work to support their families. So we have this fundamental assumption that women can't do what men have to do.

"As a country and as a world, we are not comfortable with women in leadership roles. We call little girls bossy."Sheryl Sandberg

People are always writing lists about "the next Mark Zuckerberg." Why isn't there a woman in tech who's similarly iconic? What will it take?

You could ask that question of every leadership role. Why aren't there more women senators? Why haven't we had a woman president? Why aren't there more women in computer science? I really think it's the stereotypes that become self-fulfilling prophecies.

I think we also suffer from the tyranny of low expectations. In 2012, women got 20 percent of the seats in the U.S. Senate. And all of the headlines kept screaming out, "Women take over the Senate!" And it was like, wait a minute-- 50 percent of the population with 20 percent of the seats is not a takeover. But our expectations for female leadership were so low that we were writing stories about how there was more than one woman in the Senate bathroom. Go look it up--it was an unbelievable press cycle. I just kept watching this thinking, "You've gotta be kidding."

Look, I think as a country and as a world, we are not comfortable with women in leadership roles. Our dis­comfort with female leadership runs deep. We call little girls bossy. We never really call little boys bossy, because a boy is expected to lead so it doesn't surprise or offend.

Facebook has made a concerted effort to increase diversity, but so far the needle hasn't moved very much. Is there anything you have planned to step up the campaign?

Let's be clear: Our numbers are not where they should be. The whole industry's numbers aren't where they should be. This just changes slowly. It shouldn't change slowly. I'd like to change it quickly, but there's just a lot of work to do. We have to persuade more women to go into computer science. We have to persuade more people of color to go into computer science. Those numbers are low too, although the Latino numbers have moved in the past couple of years. So we have to get more people to go into the fields, and it's the same thing with leadership.

There's been so much conversation around this in Silicon Valley in the past couple of years. Is it just talk, or is it reflecting actual change?

Certainly, conversation is the first step. Educating people on the biases is the first step.

Making the case that diversity is good for business results is really important, and I think that's getting through. What I don't talk about and other people don't talk about is, it's not that we want equality just for equality's sake, even though we do, and it's the right thing to do. It's that we also want diversity and equality because it will make our organization and other organizations perform better.

From the October 2015 issue of Inc. magazine