Why - and when - are they round?

Splashing water and soap bubbles, drops of rain or dew, condensation on the cold surface of a glass, on which to write with the tip of a finger. Games that we began to love as children and that since then, have not yet lost their charm. Games that we are 'borrowing' from the so-called 'capillary forces'. The exploration of the world of capillary forces is an inexhaustible source of wonderful surprises and amazement (not only mathematical).