Here's how Uber got its start and grew to become the most valuable startup in the world

Five years ago, a company called UberCab made a splash in San Francisco by letting you hail a car with your smartphone. Since then the company, now known as Uber, has spread like wildfire through the globe. Uber currently operates in 58 countries and is valued at over $50 billion.

But the road hasn't been easy.

Uber has fought rivals and regulators as it has transformed from a black car service into a sprawling logistics company gunning for a future of self-driving cars. It has confronted threats from the taxi industry and even its own drivers.

But its valuation has continued to climb, and it has attracted more and more investors.

As Uber bolsters its war chest for a huge push into China, we look back at how the company got to where it is today. See the insane and successful journey of Uber and its CEO, Travis Kalanick, as it has moved from an idea into a worldwide phenomenon.