So what is the story behind your avatar, anyway?
Here's mine.

Its a little girl playing in a fountain. I have no idea who she is.
Look at her face. She's filled with the joy of the moment.
She doesn't know how the fountain's pumps work, or how the rebar supports the structure. She doesn't know what the shafts or flanges for the pumping and piping underneath are rated for, and if they passed the test. She doesn't know that I and my crew tested the mechanical properties and or proof tested the piping.
She doesn't know that the steel used in the electricity generating plant, high voltage poles, structural bolts and balance of plant have test reports with my name on them.
She doesn't know that parts made from my products are on that airplane high overhead.
She doesn't know that the bolts that held her car seat secure or the engine into the vehicle that drove her to the park today are properly heat treated. Or that I signed off on the macroetch, inclusion content, tensile results or the like on the steel used to make them, as well as the springs, half shafts, injector bodies, weld studs, fasteners or a host of other parts like air bag detonators.
She doesn't know how those fittings that get machined and crimped that make up her daddy's car's brake or power steering system are fabricated. And that I was part of the decision to optimize the chemistry so that they would machine economically but still crimp successfully without cracking.
She doesn't know that I and my crew confirmed the melt chemistry of the products that hold stuff at high temperatures and pressures where her daddy works. Or that I approved the application of the material for that overhead crane and its hoist and rigging that he has to use from time to time.
She is just happy to know that daddy came home from work today and took her to the park, where she can do what's important to her, lay down in the fountain, and smile.
In her world, there is just the joy of the moment.
Because, as an engineering professional, I did my job.
I did it Right.
I did it for me.
I did it for her.
And I did it for 6.6 billion of her closest friends, who all want pretty much the same things, regardless of where they live.
This is for me what Florman describes as "the existential joy of engineering."
http://www.amazon.com/Existential-Pleasures-Engineering-Samuel-Florman/dp/0312275463
In the first place, do no harm. That's the story behind my avatar. I won't be changing it anytime soon. It continues to inspire me.
Whats the story behind yours?
milo