A lot of people credit Italian Alessandro Volta with the invention of the battery, but a discovery made in 1938 proved that the first batteries were actually much, much, much older than that—over 2,000 years older, in fact.
In 1931, Wilhelm Konig was elected as the head of the laboratory of the Baghdad Antiquity Administration. Seven years later, he noticed some curious clay jars in the National Museum of Iraq and decided to give them a thorough examination. Upon closer inspection, he found that the jars, which later became known as Baghdad Batteries, contained an asphalt stopper and, sticking through it, an iron rod surrounded by a copper cylinder. Further testing revealed the presence of an acidic substance similar to vinegar and, after replicas were produced and filled with a vinegar-like liquid, it was found that they could produce a current between 0.8 and 2 volts. Konig was then left to puzzle over the question as to why anyone would have use for such a thing in 200 B.C.
Some scientists have suggested that they were used to relieve pain, but this could be an incorrect assumption given that electric stimulation probably would have been much less effective at alleviating pain when compared to painkillers such as heroin opiate, which was also available at the time. The most plausible explanation is that they were likely used to electrically graft silver onto gold—a method that is still practiced in Iraq today.