Building block or building blocks may refer to: Building block (chemistry), a term in chemistry which is used to describe a virtual molecular fragment or a real chemical compound the molecules of which possess reactive functional groups Building blocks (toy), modular construction parts, usually made of plastic, which can be assembled in a form-fit manner Building block model, a form of public utility regulation that is common in Australia Concrete block, a standard-size rectangular block used in building construction Toy block, a wooden, plastic, or foam piece of various shapes and colors that is used as a construction toy