Instagram is living the ultimate startup dream.   The San Francisco-based upstart, which launched exclusively as an iPhone app back in October 2010, has created a new clique of photo enthusiasts.  Instagram alone boasted over 30 million users prior to its acquisition by Facebook. Now, the platform’s user base surpasses 40 million users; that’s equivalent to 5% of Facebook’s user base. When the company launched the Android version of the popular photo-sharing app earlier this month, it added an additional 10 million Instagram users to its already growing numbers in a six day time period.

What startup wouldn’t want a robust acquisition or initial public offering with a huge payoff?  Facebook acquired Instagram for a cool $1 billion in early April, and this story could not have been written any better, even if Steven Spielberg penned the script himself.

With Facebook’s Instagram acquisition still the topic of conversation in the tech space, here’s a look at why the popular mobile application has experienced tremendous growth:

A True Problem Solver

When pitching your product or startup idea, ask yourself: What problem am I trying to resolve? Instagram focused on solving the dilemma of taking strong, visually appealing photos from your mobile device and sharing them instantly. The startup does it better than any of their competitors—Facebook and Flickr included.

Perfect Your Product Before Expanding

What makes Instagram so popular is that it creates beautiful photos without the hassle of lugging around heavy photography equipment. The startup started small, focusing on Apple’s iOS platform. This allowed the company to create a greater user experience. Instagram users can utilize one of several pre-created filters or other effects to capture those shareable moments. Instagram’s decision to expand to the Android platform was done only after the team felt it was ready to advance.

Capitalize On the Desire to Share in Real Time

One might argue Instagram is what Facebook wants to be—a mobile app.  If Facebook could turn back the clock, it’s safe to say (with all the opportunities mobile has to offer)  it would launch on a mobile platform.