I was recently given a prescription for Penicillin for a throat infection and was reminded of the fascinating history of this medicine. Still in use today it was the first substance that ushered in the modern era of antibiotics that have saved countless lives. Before these drugs people would die from what we might regard as relatively minor infections. Said to have been discovered by Alexander Fleming in 1928; he was studying some bacterial cultures and found that one had got accidentally contaminated with a mould. He noticed that the mould seemed to be inhibiting bacterial growth and further investigation led to the identification and extraction of Penicillin.
Usually when things go mouldy they get thrown into the bin; it was serendipitous that he noticed the significance of the space around the mould where the bacteria were not growing. The history of discovery is littered with stories like this one; this is just one example of how being able to look at things our perceptual filters set a bit wider can let us see something important.