(you know, like how we do with maps now)
Screens are only so large, but images can be huge if we want them to be. (like this one)
It can be easy to get lost, or miss details.
(Demo some tiles.)
Used to be part of Microsoft, now there are open-source versions.
Got zoom.it open-sourced very recently - so much so that we're still working on getting it fully functional again (remember Ken's talk?)