When was the last time you got a handwritten letter?
The form of 'correspondence' has radically shifted over the past 20 years.
Today, our inboxes groan with emails, our phones and tablets ping with new messages, and colourful Snapchats with text-laden selfies explode on our screens.
Digital ephemera fills our lives, and may appear to have little value.
But for the National Library it's a powerful insight into who we are and could be valuable in the future.
Jessica Moran is the leader of the digital collection services team at the Alexander Turnbull Library, part of the National Library.
There's much more going on in an email than a letter, Moran says.
As with letter, emails can be ephemeral thoughts, a document of a decision or a discussion of ideas, but will also have attachments and - if there's access to an entire mailbox - metadata, calendars or contacts.
One of the major developments in the last few years is the open source software ePAD, a text analysis tool to pull out the names of people and organisations, or locations.
If researchers have a large file, of say 200,000 emails, the tool allows them to quickly get a grasp of what's there, and find any emails to whose content they may restrict access.
The library's web archivists and digital preservation engineer carried out a "Twitter harvest" a few days after the Kaikōura earthquake to get a sense of how people talked about the quake.
"We've always collected things like newspapers which are often that first reported version of an event but with Twitter we also get it from ordinary, everyday people
"So it really diversifies the collection of content around that event that we're able to capture."