FlowPane lays out its children in a flow that wraps at the flowpane's boundary.
A horizontal flowpane (the default) will layout nodes in rows, wrapping at the flowpane's width. A vertical flowpane lays out nodes in columns, wrapping at the flowpane's height. If the flowpane has a border and/or padding set, the content will be flowed within those insets.
http://docs.oracle.com/javafx/2/api/javafx/scene/layout/FlowPane.html