Content Elements (http://www.krea.com/content-elements) is an ExpressionEngine fieldtype created by Krea.

Content Elements (http://www.krea.com/content-elements) is a fieldtype for ExpressionEngine that gives your clients the freedom to create content structure directly on the publish page using 'Content Elements'. You will no longer need to create individual channels to accommodate different field groups. Instead, you can let clients choose what content elements and what order to use — all in one channel and using a single field type.