Herodotus's most famous work is also the only work of his that is known to historians in our time. Its title is simply The Histories.
This work is a discussion of the causes of the wars between the Greeks and the Persians that had before Herodotus was born as well as during the very early years of his life. The work also discusses the histories of Persian kings from before the wars.
Because of this work, Herodotus is known as the "father of history." This is because he is the first person who is known to have written a history in what we would now see as an objective way. He collected a great deal of information about his subject and tried to think about the extent to which it was all accurate. He then set out his conclusions in a logical way.