Researchers have taken to recycling laboratory helium in the face of dwindling supplies resulting from the blockade of Qatar (Nature 547, 16; 2017). Such extreme situations have also prompted other scientists to devise imaginative alternatives in the past.

In the First World War, for example, German naval blockades caused a shortage of acetone and butanol, both essential for munitions. Chaim Weizmann at the University of Manchester, UK (a scientist who later became president of Israel), promptly invented a process for making both chemicals in bulk from starch fermentation using the bacterium Clostridium acetobutylicum.

And a British naval blockade, in turn, propelled German scientists into hijacking another fermentation process to create glycerol, needed to synthesize the explosive trinitroglycerine. They used bisulfite to divert the fermentation of sugars in yeast into glycerol instead of ethanol (go.nature.com/2vkvq7k).