Millions of people on Earth start their day the same way: we get out of bed, go to the loo and wash ourselves. But this hasn’t always been the standard routine. Ancient Greeks and Romans were happy to splash about in public baths, but by the time the plague struck 14th-century Europe, many people believed that water spread diseases. It was not until the 18th century that Louis Pasteur proved that dangerous germs actually lurk in dirt. Even when hygienic habits began to be taught in schools, lessons were limited to washing faces and hands, because those were the parts that everyone could see.