Comics is a medium used to express ideas with images, often combined with text or other visual information. 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; fumetti is a form that uses photographic images. Common forms include comic strips, editorial and gag cartoons, and comic books. Since the late 20th century, bound volumes such as graphic novels, comic albums, and tankōbon have become increasingly common, while online webcomics have proliferated in the 21st century.