How can you zoom in on text within an iframe?

I'm creating a text editor with an iframe that has the contenteditable attribute on. I added a zoom feature, that zooms in on the iframe. Here's the code: document.getElementById("textareathingy").style.zoom = percentage; When I use the zoom in feature, it makes the iframe "bigger" but the size of the text remains the same. When you use Google Docs, however, their zoom in feature also zooms in the text. Can someone point me in the right direction to make the text within the iframe also be zoomed in.