One of the first “fun facts” I can still remember hearing as a child is that every drop of water holds as much life as the number of human beings on the planet. Whether or not this is exactly true I don’t know, nor do I have any idea what was meant by “life” in this context. Is its metric the single microorganism? And are there really several billion micro-organisms contained in every water drop? Surely there must be a difference between water from the kitchen tap and water from a muddy pool.

However lacking in accuracy, the factoid floated to mind when I visited Marjolijn Dijkman and Toril