Hey scientists, here's a fun game for your readers: include a scale bar in a figure, but don't say how long it is!
1cm seems sensible? No that would make this thing to small ... 10cm?... no way too big. Okay, it's a bit of a strange number but 5cm? Nope still too big. I think it's 3cm.
The great thing about this game is that you don't know you've got the right answer! Hours of fun!