A small message on a big poster - a figure of speech on how the smallest things (even the tiny ones we need the help of a special instrument to see them) can have a huge impact in our lives. Just a representative that the smallest things can harm us. Since we can’t see them we don’t pay much attention to them. There’s nothing to pay attention to. The scale is different and we have trouble imagining it. The big green paper is not “clean” or blank anymore even though you need to observe very closely to understand that there is some tiny message on a big A0 poster. This is how germs work as well, we can’t see them, but they are there!Keeping hands clean is one of the most important steps we can take to avoid getting sick and spreading germs to others.