Some widgets serve a higher purpose: they organize and present other widgets. These widgets are called ~containers~. This means that they may contain one or more of other widgets and control their relative layout as well as present some decoration alongside the contained widgets. Examples: vertical box horizontal box table button The contained widgets are container's ~children~. Containers usually respond to resize events and addition and removal of children by reallocating the available space among its remaining children. Since a container is also a widget, we can nest containers to an arbitrary degree: a vertical box containing a table containing a button containing a label.