Breakpoints are the point at which your site's content will respond to provide the user with the best possible layout to consume the information. A breakpoint separates the height or width of viewports (screens, printers, and other media output types) into steps. For instance, a width breakpoint of 40em creates two steps: one for widths up to 40em and one for widths above 40em. Breakpoints can be used to define when layouts should shift from one form to another, when images should be resized, and other changes that need to respond to changes in viewport height or width.