I'm Carla Zeus, introducing Part two of our four part series on Facebook.

The highly successful and controversial company is celebrating its 15th birthday this month, and on the heels of yesterday's report that focused on its founder, today's special examines the decisions that were made that grew the company into what it is today and contributed to some of the challenges it's faced.

The social media application didn't always look like we know it today used to be more static.

If you wanted to see what someone was up to, you had to click on his or her profile.

Now, of course, information is fed to you.

But what's become a defining part of the product has had a bumpy road breaking and developing news stories, or just a click away at CNN dot com.

Meantime, for us, Laurie Siegel takes us back inside a social media behemoth.

It was June 2006.

Yeah, who offered a $1,000,000,000 to buy Facebook.

At the time, it seemed almost incomprehensible.

Most of the management team really thought that we should sell.

I remember had one late night conversation with one of my closest advisers, where He sat me down.

It was probably 11 o'clock and he said, Mark, if you don't sell the company, you're going to regret this decision for the rest of your life.

It was just really intense.

What'd you think when he said, Um, when Dustin and I made the decision to not sell the company within 18 months, every single person on the management team left.

Did you ever question yourself that you're making the right decision?

Oh, yeah, because I mean, I was 22.

I didn't I didn't have an exact plan of what was gonna happen.

Was incredibly scary.

It was it crazy, arrogant, confident.

It's all of those things on, and that is the curse of the autocrat.

It is.

This wild cocktail of vision will power a little bit of arrogance, a little bit of confidence and saying, you know, thank you, but I believe something else and arrogance or perhaps hubris that many have said let Facebook into some of the serious troubles it's facing now.

But then it was the vision for what would come next that played out three months later, September 2006 the birth of news feed people would simply go to somebody's profile.

Then they will go to the next person profile in the next person's profile and Facebook like Ah ha, we need to actually bring this altogether and just show you what's going on with your friends, especially those friends that are most important to you.

And that was, of course, the dawn of the now famous algorithm news feed would completely overhaul the site, giving a real time feed of your friends and your family here.

I'm gearing up for this fantastic launch and all the engineers air so excited.

Facebook's former PR director remembers how everything changed.

In a minute.

We saw these this group that became a 1,000,000 people protesting against news feed using news feed.

The backlash was extreme.

The phone started ringing off the hook.

Thousands of emails of people saying, What have you done?

What have you done?

What have you done to my Facebook?

I think they were sort of alarmed by Facebook, taking their activity and publishing.

It was one of these first privacy scares on Facebook, but newsfeed survived, and it thrived, ultimately became the thing that is a core of Facebook, the new speed.

It's not one of the course Facebook.

But it's the core of every social media application used.

It was Facebook's firsthand to privacy issues down the line.

The stakes on Lee got higher as the platform connected the world.

Welcome to December 2007 also known as that time Facebook ruined Christmas.

There was a guy who bought a diamond ring for his wife and all of his friends.

It flashed up on there, including his wife.

Christmas ruined, he said.

It was Facebook's first big privacy scandal.

Thousands were outraged.

We're really ticked off, ticked off by Facebook's first real attempt at making money.

It was an ad product called Beacon.

Facebook User can log into e commerce sites using your Facebook identification.

And then when you buy something, all your friends are gonna find out about it.

And Facebook was like, This is such a cool, innovative way to get involved in commerce and not be doing boring old advertising.

To say they got it wrong was an understatement this soon after the news feed outrage.

But like many bed Zuckerberg made that paid off, this was different.

Story of Facebook.

Beacon is the time for Facebook, really.

It was a privacy and PR disaster.

It took the company a month to react.

Facebook yesterday apologized and said that now you can entirely opt out of this program.

But the loss of trust was damaging.

It was officially time to bring in the operator that many believe Zuckerberg needed to help run Facebook.

That person was Cheryl Sandberg.

A time You're 38 years old, you're managing 4000 employees at Google, leaving for a company that barely had any revenue and you felt like this was the opportunity.

I felt like this was a great opportunity.

A lot of people said to me, What are you doing?

Facebook was really small.

It didn't seem to be growing that quickly.

And I told them I'm goingto work with and for someone I really believe in, who I think is trying to do something really important those early years was Cheryl at the helm would lead to tremendous growth, as would Facebook's next move.

It would eventually be called platform.

It was the first time that Facebook waas opening the site to allow outside technology companies and or in certain cases, individual developers to build something that would work with the site.

It would prove to be one of the most important moves the company made and down the line would lead to fundamental questions and concerns about how the company handled user data giving third party developers thehe bility to create their own applications by accessing Facebook user data.

Facebook platform is why you can follow your friends play lists.

It's why you can see your friends birthdays on your calendar.

And remember, I think the early form of platform was sharing more data.

The architects were focused on the good as it went live in 2007.

It was a money maker the moment it went live and would lead to tremendous innovation and growth.

But years later it would become the root of one of the company's biggest scandal.

So there's always a Catch 22 whenever you're giving a voice to people who didn't have a voice before.

They soon discovered policing content was complicated, an issue that would only grow as Facebook group and moving into 2012.

Zuckerberg was close to a 1,000,000,000 users and gearing up for the company's massively anticipated AIPO questions Air coming out.

Is Facebook really living up to the hype.

But there was a problem.

Smartphones were on the rise, and Facebook wasn't a mobile first app.

It was easier to access it from a computer.

So Zuckerberg did something atypical.

He bought a company during what was known as the quiet period.

Why the need to go on a buying spree?

It was really connected to this whole transition to mobile phones being the main way that we use technology.

Instagram was one of the most downloaded applications on the iPhone.

Zuckerberg went out and just put like, humongous money about the money on the table and bought Instagram.

Everyone said, You're crazy, What are you doing?

That's a bad idea.

And actually throw turns out to be brilliant $1,000,000,000.

They think there are a lot of people that doubted whether or not this was really a good acquisition.

And if you look back now, it makes so much sense.

It was an investment in Facebook's mobile strategy, and it helped the company bolster its portfolio ahead of the I.

P M.

Facebook is set to go public this week in what could be the biggest AIPO in history.

Going public is an important milestone with the world watching everything that could go wrong went wrong.

Stock that maybe picked a bad week to go public.

Facebook spaceplane.

The beginning of the wildest period, the stock tanked and continued to for 100 and nine days.

I mean, it was the definition of roller coaster in every way.

And during all of this, the one person we didn't hear from was Mark Zuckerberg.

It was echoed a tiny little bit.

You know, when Mark and Cheryl were acquired for three plus days after the Cambridge Analytica crisis, I think market the time just very firmly believed that we're gonna focus on building our stuff instead of talking about our stuff.

Until Zuckerberg spoke for the first time at this point, it was a highly anticipated interview.

Welcome to TechCrunch.

Disrupt.

And thanks for coming.

Thanks for having me.

This is a defining moment.

Your ice skaters stepping on for the long skate and you know, you gotta nail it.

Performance of the stock has obviously been disappointing.

We already see that mobile users are more likely to be daily active.

Users of Facebook said, you know, we're gonna be focused on mobile and anyone who doesn't bring to my office mocks prototypes that are based on mobile rather than desktop will be kicked out.

We have almost 500 million mobile users.

They made the shift and it would pay off.

Eventually, the stock price went up.

Zuckerberg's bed on Instagram also paid off in a big way.