It’s finally arrived.  One of the most anticipated public offerings in the past decade, Facebook’s filed its S-1 for an IPO.

The massive social networking site has reached millions around the world, revolutionizing the way we communicate, manage relationships and do business.  As Facebook shifts from a privately held company to a publicly-scrutinized organization, some interesting numbers have emerged: Facebook has 845 million users and 483 million daily users, annual revenue of $3.7 billion, $1.8 billion in operating income and $1 billion in net income.

It’s IPO today sets out to raise $5 billion.

The now-public Facebook faces many challenges ahead, expanding its monetization solutions and corporate responsibilities.

But what started out as a snarky project by a Harvard student didn’t begin with the intention of becoming such a world-renowned brand.  In a letter to investors, Facebook founder and CEO explains:

Facebook was not originally created to be a company. It was built to accomplish a social mission — to make the world more open and connected.

We think it’s important that everyone who invests in Facebook understands what this mission means to us, how we make decisions and why we do the things we do. I will try to outline our approach in this letter.

At Facebook, we’re inspired by technologies that have revolutionized how people spread and consume information. We often talk about inventions like the printing press and the television — by simply making communication more efficient, they led to a complete transformation of many important parts of society. They gave more people a voice. They encouraged progress. They changed the way society was organized. They brought us closer together.

Today, our society has reached another tipping point. We live at a moment when the majority of people in the world have access to the internet or mobile phones — the raw tools necessary to start sharing what they’re thinking, feeling and doing with whomever they want. Facebook aspires to build the services that give people the power to share and help them once again transform many of our core institutions and industries.

There is a huge need and a huge opportunity to get everyone in the world connected, to give everyone a voice and to help transform society for the future. The scale of the technology and infrastructure that must be built is unprecedented, and we believe this is the most important problem we can focus on.

We hope to strengthen how people relate to each other.

Even if our mission sounds big, it starts small — with the relationship between two people.

Personal relationships are the fundamental unit of our society. Relationships are how we discover new ideas, understand our world and ultimately derive long-term happiness.

At Facebook, we build tools to help people connect with the people they want and share what they want, and by doing this we are extending people’s capacity to build and maintain relationships.

People sharing more — even if just with their close friends or families — creates a more open culture and leads to a better understanding of the lives and perspectives of others. We believe that this creates a greater number of stronger relationships between people, and that it helps people get exposed to a greater number of diverse perspectives.

By helping people form these connections, we hope to rewire the way people spread and consume information. We think the world’s information infrastructure should resemble the social graph — a network built from the bottom up or peer-to-peer, rather than the monolithic, top-down structure that has existed to date. We also believe that giving people control over what they share is a fundamental principle of this rewiring.

We have already helped more than 800 million people map out more than 100 billion connections so far, and our goal is to help this rewiring accelerate.

We hope to improve how people connect to businesses and the economy.

We think a more open and connected world will help create a stronger economy with more authentic businesses that build better products and services.

As people share more, they have access to more opinions from the people they trust about the products and services they use. This makes it easier to discover the best products and improve the quality and efficiency of their lives.