Shape poetry, also known as concrete poetry or calligrams, is a type of poem where the physical layout and form of the words is part of the intended meaning. There are two main types of shape poetry: outline poems, where the lines of words form an outlined shape related to the topic, and drawing poems, where the lines of words are used to create the lines of a drawing. The ancient Greeks are credited with enhancing poetry by arranging words in visually pleasing ways as early as the 3rd-2nd centuries BC. In the 1950s, a group of Brazilian poets called Noigandres held an exhibition of their work and defined concrete poetry through a manifesto stating that the structure of a poem is its content.