And we've got something special we're launching today.

It's a four part series that'll air through Monday, and its focus is on Facebook.

More than 1/4 of the entire world's population.

It's said to log on to Facebook every month, and it's grown toe have 3.2 billion users in just 15 years.

In fact, it was 15 years ago this month the social network was launched.

The milestone birthday for the momentous company gives us the chance to discuss its huge scale successes, and it's huge scale failures.

Its founder alone has pledged billions of dollars to charity and then accused of copying the very idea Facebook was built on.

As always, CNN dot com will have full coverage of breaking and developing world news in the days ahead.

As we begin our first of four specials on Facebook, we're starting with a report on the man behind it.

It's October 1920 18 and we are heading to Facebook.

This is a really big deal.

We're going to sit down with Mark Zuckerberg, who rarely sits down for interviews.

Facebook years are like dog ears.

A lot happens in a little time.

In the months since I first walked through these doors, nearly 50 million Facebook users have been targeted by hackers, the largest security breach in Facebook history.

Facebook on the defensive today and we'll get all that later.

But for now, back to Facebook and what you need to know about an interview with Mark Zuckerberg.

It's super cold.

First, he likes a room cold, very cold.

Turned the cameras around, and you'll see his people on the other side there, taking notes, scribbling furiously, Keeping time.

They know that the stakes are high these days.

The whole world seems to be watching, and that's Facebook.

In this current moment, Thank you for coming.

Massively influential Facebook CEO Mark Zuckerberg under fire in flux.

Biggest security breach in the history of Facebook and controversial.

But to fully understand Facebook of today, you have to go back to the beginning.

Hi, I'm Mark Zuckerberg, founder of Facebook and online social Directory.

That was really just stare in the camera.

Just give it to those quirky thanks.

The early days of Facebook, her very scrappy time.

There have been some constants through the years here.

The mission of the company of connecting people and bringing people together.

That really has informed some of the most important decisions that we've made.

You're going to hear this phrase the mission quite a bit.

Mark's mission is the mantra at Facebook.

Our mission has really always been to connect the world were a mission driven company.

Our mission is to connect everyone in the world connect, connect.

We can connect the whole world.

It was in the company's DNA from the beginning.

I think that people have been drawn to this company over the years or people who really care about that.

If you're unemployed, you hear it.

The moment you walk through the door, you're almost indoctrinated into it.

He believed in the mission of Facebook.

Thio.

Help people share and be more connected, and I wanted to follow him.

It just felt so different from anything I've done before.

Mark had this vision that everyone could be connected, and that was pretty exciting.

What's on your mind?

Inside Facebook headquarters, that message to build out the mission is everywhere.

Inspirational quote posters line the walls with delicate phrase is fine tuned to Facebook's current stay.

Some call it almost even like a cult.

Is this the cult of Mark Zuckerberg?

I think a cult of personality is a little bit more kind of a Steve Jobs.

Oprah Winfrey, Bill Clinton territory.

Maiko Finger worked at Facebook for six and 1/2 years.

Think cult of mission is what Facebook is, and that is still very much around.

And that's why people look to join Facebook.

Full formal mission statement is gonna be.

The mission is clear, as is one other thing toe.

Understand Facebook?

At 15 you have to understand its DNA and its DNA is Mark Zuckerberg after just spending his entire childhood growing up with three sisters.

He's like, I just got to connect with other people.

Mark's older sister, Randi, rarely gives interviews about her brother and Facebook.

We were always inventing, were always collaborating.

We're always like looking for any technology we could find and using it to just, you know, create something bigger.

Yeah.

What?

I got accepted.

Are you serious?

Yeah.

All right.

Creating solutions to problems yet to be seen was in the Zuckerberg blood and would eventually morphed into the mission when Mark left home wear now focusing on one of the newest members of Harvard's class of 2006 its roots were actually quite trivial and controversial.

Marks First project at Harvard was Face Match was a hot or not style site he created by hacking pictures of classmates from Harvard Storm, a Torrey I.

D Files.

People could rank C two pictures of people who are students at Harvard and vote for which one was more attractive than this site, then produced a list of the most attractive people in at Harvard.

Wrecked business Insider Global editor and chief Nicholas Carlson, obviously very offensive people got very upset for it, and Zuckerberg was hauled in front of the disciplinary board at Harvard and admonished for this.

But same time, that project revealed that Zuckerberg completely understood what people wanted to do in social media.

What do you mean?

What I mean is, is that people?

When they voted, they ended up voting on average 44 times, which means they were like addicted to the programming, a platform that played into the best and worst of human impulses that became familiar later.

But in the meantime, it didn't take long for Harvard to shut down the site.

Mark actually became a celebrity of sorts on campus E.

I was like, Oh, Mark, like, you know, you gotta probably put that out there and didn't really think it through that well, But I mean, he always saw a need for something, and his gut instinct was always like, Let's get this out there and then make it perfect.

This'd idea of creating and breaking in the name of connecting would be a theme that would only amplify a decade later as the stakes got higher.

But 15 years ago at Harvard, it motivated Zuckerberg's next life changing creation.

Somewhere along, one of these pathways might have been where the idea for Facebook started.

Harry Lewis was Mark's computer science professor and a dean at Harvard.

When Mark and every other student arrived on campus every fall, they were handed a Facebook, literally a book of faces and names and hometowns.

Basically, that's all it is.

There were some computer science students who were year to put, you know, the Facebook Online.

This is not necessarily a simple thing to do, and then somebody did it anyway.

Okay, without her, without our involvement, that somebody Mark Zuckerberg, he walked up to the registrar's office.

Can I help you?

And volunteer is a student to digitize this.

And they just said no.

And I think it was almost a little bit of like, Well, maybe you just don't get what I mean.

So let me just go home and do it and show you I want to meet that person who said no and give them a hug because if they had, you know, have the business foresight to say yes, like none of this would have ever been created.

February 4th, 2004 Facebook went live within 24 hours and estimated 1200 students had signed up.

Within months, they had 100,000 users.

A pretty meteoric rise.

Who knows where we're going next?

Mark's mission was born.

He was just 19 years old.

We're hoping to have many more universities by fall, hopefully over 100 or 200.

And doing that would require a move to the epicenter of tech Silicon Valley, where Mark found more space, more money and more controversy.

What was the deciding factor for leading?

Why made Facebook Summer 2000 for Mark and his co founder, Dustin Moskovitz, left Cambridge and moved to Palo Alto a time the site was exploding a 1,000,000 users and the company had little money in the bank.

So the crew was making the Silicon Valley venture capital circuit and their own way.

Here.

These famous stories of Zuckerberg and his team going toe V.

C's in their pajamas and showing up late and being kind of rude.

He was very like I'm young.

Rules are for adults.

Get to work late.

Just do your thing.

Coated Hackett in overtime.

You know, they used to have a sign on the wall, which is like, Move fast, break things.

And it's like now it says that I can move carefully and don't break.

It's rather and such a delicate like don't break break things.

Sometimes you break the country.