How to Zoom In on an Email in iPhone Mail

My kitchen scale is very sensitive.
It is a beauty: stainless steel shines gently around its soft corners and large black numbers flash up reassuringly — whenever you close the fridge, put down a pot next to it or, I guess, breathe in its vicinity (I do not dare to).
It sure would be nice, sometimes, for my sensitive kitchen scale to focus a bit more on real mass on its pan and less on the minuscule shaking hard to avoid in a cooking place. iPhone and iPod touch are, of course, sensitive to touch as well; and you can use that to zoom in on the real content:
›› Text not legible? Image too small? In iPhone Mail, you can enlarger portions of your emails with a couple of taps.