Comics is a medium that expresses narratives or other ideas using a series of still images, usually combined with text. It typically takes the form of a sequence of panels of images. Textual devices such as speech balloons, captions, and onomatopoeia can indicate dialogue, narration, sound effects, or other information. The size and arrangement of panels contribute to narrative pacing. Cartooning and other forms of illustration are the most common image-making means in comics.