Who wrote the books behind the Harry Potter-films?

Explanation

The first book about Harry Potter was published in 1997. The series is written by J.K.Rowling and became so successful that it was only a question of time before they were being turned into films. The films also enjoyed tremendous success. The first film, 'Harry Potter and the Philosopher's Stone' already saw the day of light in 2001. Since then, altogether 8 films have been made about the young wizard. To create variety in the films, five different directors have been involved in the 8 films.