Correcting myself, I was thinking of Zinc Oxide. But it's still pretty inert. I wouldn't want a plate of it, but whatever level of toxicity it possesses, it is low enough that it requires careful study to detect.
I thought the trick was you spin the egg, then stop it - a raw egg will continue to rotate because the fluid inside is moving, but a cooked egg won't restart because nothing inside it is moving.
It is a function - print() is being called as a function, taking a number of positional, arguments followed by named argument. I don't think you're correct about this being special syntax, except for the '*' is being used to expand a list into the positional arguments.
In the simplest configuration have a X-Y stage that you raster, along with Z axis control - generally these are all piezo controlled. Your signal is then acquired by maintaining a constant tunneling current while you raster, so you track the Z axis position as you raster.
This means that you're getting a "pseudo-height" map - if you had a surface with 2 types of atoms, both the same size, but with different tunneling barriers, you would see them appear to be different sizes.
Thanks for that pointer - that is a seriously cool channel - I wasn't sure what to expect, but I'm really digging the videos discussing how to correctly assemble a jet engine.