According to Google lore, a user "kvetched about spending all her time filing messages or trying to find them," and asked Google to solve her email woes. This led an engineer to start working on the service as a "20% time" project, company-slang for employees' passion projects. Gmail would famously stay in beta until 2009, five years after launch.

2006 was a year of rapid expansion for Gmail. Google launched chat in February, Gmail for domains three days later and Google Calendar in April.

The August 2010 launch of Priority Inbox separated incoming mail into three folders: "Important and unread," "Starred" and "Everything else." The service intended to help users bogged down by subscription emails

The massive design update in 2011 was Google's first real attempt at reducing visual clutter. Profile pictures were added to conversations, HD themes were added and the option to display your inbox as "comfortable," "cozy" or "compact" helped users with different screen sizes.

The latest visual update separates incoming emails into separate tabs, further reducing inbox clutter and sparing users the stress caused by an endless stream of email notifications from social networks.

Gmail got its first Android app in 2008. It was made available for T-Mobile's G1 phone. Today, the app has been downloaded on Google Play close to a billion times.

The long-awaited Gmail app for iOS devices arrived in November, 2011. The app has been regularly updated ever since, now allowing users to switch between up to five separate accounts.