Serendipity, which means “valuable discovery by chance,” sometimes occurs in science and technology.  （1）A typical example is the accidental discovery of penicillin in 1928.  Instead of throwing away a moldy sample as he usually did, Dr. Alexander Fleming, a Scottish bacteriologist, examined it closely and discovered an antibiotic substance capable of killing many bacteria.  （2）Another example is the chance discovery of insulin in 1889.  While studying the role of the pancreas in digestion, two German physicians removed the pancreas from a healthy dog and later happened to see a large number of flies attracted to the dog’s urine.  They realized that the dog was secreting sugar in its urine, a sign of diabetes.