The idea for the Internet has been around 25 years, and email attachments have been around almost as long.
Almost exactly 22 years ago, researcher Nathaniel Borenstein sent the world's first email attachment: a picture of his barbershop quartet, the Telephone Chords.
Borenstein, along with another researcher named Ned Freed, wrote MIME (Multipurpose Internet Mail Extensions) because one day he hoped to get pictures of his grandchildren over email. To the delight of grandparents everywhere, his technology became ubiquitous; MIME is still used for every email attachment, and has spread to host content all over the web.
Take a look at the picture over at Quartz, which also has an interview with Borenstein.