How long have you had your Gmail address? Longer than you've been at your job? Longer than your current relationship? At this point, Google's free email service is nothing less than an internet institution. As we look forward to seeing how it will continue to evolve over the next 20 years, we're witnessing the Gmail Android app pass a significant milestone, as the Play Store tallies up 10 billion installs.

Granted, Gmail comes preinstalled on a lot of Android devices, but we're not about to let a little thing like that take away from this accomplishment. Gmail is just the latest in a string of core Google apps that have already crossed the 10B threshold, starting with Play services and followed by YouTube and later Maps. Along with Search (thanks, Igor!) and now Gmail, these are the only four five Android apps to have ever reached this lofty height.

What's going to be the next Android app to hit 10 billion copies installed? Chrome sounds like a likely candidate It's probably safe to say that Facebook will be the first non-Google app to join the club, but will it get there ahead of Google's ubiquitous browser? We may be finding out in just a few more months.