Low level graphics and you

After a long time of meditating on OpenGL I've come down with a bad case of "I don't know how to do anything and only use tools made by someone better than me". Since the only cure for this common programmer illness is more meditating I've decided I want to learn graphics on an even lower level than OpenGL, though finding a guide for this route has proven to be nigh impossible.

I'd appreciate it if a guru could give me a friendly pointer in the right direction or an insight on the things that take place between an OpenGL call and a pixel being displayed onscreen.

At the end of my journey I desire the ability of displaying but a single pixel without the aid of instruments given to me by the masters.

Please read the 1st post before replying.
I'm already proficient with OpenGL and GLSL, what I want to know is how graphics libraries are written in the first place. To put it as simple as possible, what would be the universal low level equivalent(assuming there is one) of glVertex.