For everything we think we know about Marvel, there's somehow always more to learn.

The '60s represented a crucial time for Marvel, so any chance to take a look behind the veil during that era is a welcome one. And this letter from then staff writer Dennis O'Neil to a young fan is actually more revealing than you'd expect.

First, a little context. By 1966, most of the Marvel heroes you know and love were already created and thriving, and had been for a few years. The X-Men were still struggling, but other than that, things were swimming along nicely under the guidance of Stan Lee in his prime. There was a small but strong team of staffers and a slew of freelancers.

That's the usual snapshot of the times, but O'Neil's letter takes us a little deeper.

The history of Marvel (abridged, naturally) gives us the tale we usually hear about the struggling times for the comic industry and how Lee's portrayal of the Fantastic Four as flawed humans more or less saved everyone's collective bacon.

But a few things of note emerge, most notably the comments concerning the Jack Kirby art from Fantastic Four #46 that was included with the letter. O'Neil explains that the notes on the side of the pencils are Jack's because he "plots the story as he draws it."

In the ongoing discussion over just how involved Kirby was in the writing of the books he drew, that's pretty definitive, though it's also worth keeping in mind that O'Neil insists the "whole operation is based on the story instinct" of Stan Lee.

There are a few mentions of adaptations, too. The '60s animated Cap that would debut that year was described as "being shot in an animation process similar to that used by Hanna-Barbera." Even more interesting is when O'Neil mentioned that "a producer named Robert Kranz is interested in the live television rights to several Marvel heroes”.

A live-action Marvel series, eh? Nah -- that'll never work!

Check out the letter in full in our gallery below. It's pretty neat, and Kirby's pencils, as ever, are among the best that comics have ever seen, even to this day.

(via Sean Howe)