Accidental oddity.

The intent was to be something completely different - BUT . . .
I peered down into a freshly washed, but un-rinsed milk bottle and saw a rather fine example of "hexagonal close packing" of bubbles, all of which must have been about 1-1.5mm diameter.
I selected macro, paused close to neck and clicked.
Could not work out what I was seeing in the result.
THEN  
I worked it out - the camera was way too close to said bubbles and had looked "past" and focussed on a reflection seen in a lower, larger, bubble film(s) with the window panes' divider very clear.