We all known how clouds can look like living things such as fantastical animals and the faces of B-list celebrities, but it now turns out that, in one sense at least, they actually are alive. Living microoganisms, such as certain types of bacteria and tiny particles of lichen, have been found up in the droplets of clouds. Blown into the atmosphere from the ground by the wind, these organisms happen to be just the right shape to encourage water droplets to freeze. This has led scientists to speculate that they might play a role in encouraging the clouds to rain, thereby returning down to earth in the raindrops. Are these natural bacteria using the clouds to get around? Known as 'bioprecipitation', this is an exciting new frontier in the study of clouds.