Imagine a family of Soviet immigrants that were allowed a temporary stay in the USA with minimal allowance. With only food stamps separating them from starvation, they have to live almost like Spartans. What are the odds that a child in such a family grows up to be a billionaire?

Perhaps fate smiled down on Jan Koum to inspire belief in hundreds of thousands of others, and show that nothing is impossible. After all, nearly everyone reading this had far better opportunities to start with than Mr. Koum.

2014: Mountain View, California, USA

The white façade of the building they just walked out of is not unfamiliar to Jan Koum, for it was once the Social Assistance office. Over 20 years had passed since he was last here for food stamps. Today, in this very building, he completed a legendary deal, selling his company for $19 billion.

1991: Fastiv, Kiev Oblast, Ukraine

His parents began thinking about emigration two years prior, when life in the remote village became utterly bleak—store shelves emptied for good, while hot water and electricity alternated between appearing and disappearing. Also around this time, Jan had been taking extra English lessons with his tutor. And so, everything fell into place—Jan and his mother set off to the United States.

1992: Mountain View, California, USA

Their tiny apartment included two beds and a bare minimum of everything else. At least the Koums stocked up on clerical objects in their homeland—the pencils and journals would last them a long time. The accommodation was provided to them by the social assistance center. His mother was very sick, but didn’t have the money for medicine. Her disability benefits and the little she earned babysitting were not enough to make ends meet.

After school, 16-year-old Jan worked as a janitor, and eagerly read everything he could about programming. His rare instances of free time were spent in bookstores; although he couldn’t afford the books, it wasn’t illegal to read them and put them back on the shelf. By the time he turned 19, Koum was a real programming ace, and soon after joined the hacker group known as w00w00.

1997: San Jose State University, California, USA

The young immigrant and talented hacker finally had a stroke of luck—he managed to not only enroll in university, but also to find a job in the information security department at Ernst & Young. But perhaps the greatest fortune at the time was his meeting with Brian Acton. Acton was the manager of Yahoo (the largest search engine at the time), and invited Koum to the testing of its new advertising platform.

Of course, it isn’t easy to juggle a job at a large firm and university studies. Every urgent call during lectures set Koum back, and oftentimes he was simply unable to be of aid. The fact that he couldn’t do everything at the same time frequently irritated him. He wanted to be able to both pay attention to the professor and fulfill his duties as an information security engineer, or practice boxing while staying connected with his colleagues. When he felt he simply couldn’t solve this dilemma, he dropped out of university to dedicate the coming years to his job at Yahoo.

2008: Somewhere in South America

Although working at Yahoo brought about a decent income, there was no happiness to be found at the job. Brian Acton and Jan Koum, people of wildly different character and temperament, both hated the advertising, long negotiations, and marketing games—everything they considered to be “corporate rubbish.” Upon saving enough money, the two friends quit their jobs and set off into the free market. They traveled and deliberated their future. They even tried to get a job at Facebook, to no avail; athough judging from Acton’s twitter, they weren’t too disappointed.

Jan Koum — Founder of WhatsApp and slumdog billionaire

Their carefree adventures continued until Jan Koum first laid his hands on an iPhone. It wasn’t the device that truly piqued his imagination, but rather the apps and their endless possibilities.

2009: Silicon Valley, California, USA

While noisy parties raged in the living room, the two programmers could always find comfort in the kitchen, discussing the possibilities of the contact list on their phones. Jan Koum noted that it’s useful not only to see someone’s phone number, but also their status. Are they busy? Is their battery dead? Perhaps they share your eagerness to have a stroll in the park or a bike ride along the coast?

The name for the app came easily. It’s common to ask someone “What’s up?” as a greeting, so, naturally, “WhatsApp” was a name fit for the App Store.

WhatsApp’s First Steps

Koum was captivated by the idea of global, borderless communication without the need for a computer. Everything you need to find out how your friends and family are doing fits right in your pocket. Although mobile versions of various apps like Skype exist, they require a login and password; for WhatsApp all you need is your phone number—how convenient is that?

After several months of tedious work, the app was ready. However, only friends and colleagues wanted to download the app initially. All of their complaints and suggestions were written down in those very same journals Koum brought with him to the US all those years ago. He never got tired of tweaking and polishing the app, but their flat-out rejection of advertising meant the app didn’t see mass downloads. At one point, Koum was ready to give up. Brian Acton talked him out of it, “Be a little more patient, you’d be stupid to quit now.”

His friend’s advice proved useful: within a few months, Apple added the ability to receive instant notifications from apps in a new iOS version. This worked exactly into Jan Koum’s concept of always being informed and connected with your contacts.

People started to mess around with the app, setting statuses like: “Just woke up”, “Off to breakfast”, and, of course, “What’s up?”. This proved to be very comfortable, and, most importantly, completely free—after all, Koum was never preoccupied with how much money he’d make. To him, the most important things were how many people used the app, and whether they liked it.

WhatsApp: A Huge Success

Jan Koum — Founder of WhatsApp and slumdog billionaire

2010: The number of users rose to 250,000 in just a few months. Brian Acton joined Koum’s exciting project, and the two began thinking of new possible features. One such feature was something completely unique at the time: the ability to see whether your message was delivered and, subsequently, seen. They also added MMS functionality, a feature that never really gained traction in the past, but tied in perfectly with WhatsApp’s instant messaging concept.

2011: WhatsApp took off and quickly cemented itself among the most popular apps on the App Store. And—just as before—with no advertisements; Koum and Acton remained fervent opponents to the idea.

In February of 2013, WhatsApp’s active user base grew to 200 million—today, there are over a billion.

In just 4 years, WhatsApp became a record breaking sensation in terms of growth, passing even Facebook.

The project’s success grabbed the attention of many large businessmen. Facebook bought WhatsApp not only for an incredible sum, but also with solid terms: the WhatsApp team retains independence of their brand, working autonomously; the team are provided the necessary infrastructure; and WhatsApp has no ads, just as before. The terms were tailor-made for the founders, who were vocal about their dislike for corporate meddling. Jan Koum subsequently entered the Facebook board of directors, and became their second largest shareholder after Mark Zuckerberg.

Today, the app is available to users in over 50 languages and across all major mobile platforms. Every day users exchange 40 billion messages, photos, and videos.

At this point, it won’t be surprising to see WhatsApp set new records. After all, it wasn’t created to make profit, but for an idea: to make communication more simple and accessible.