Building blocks are materials used to construct structures. CINDER, ADOBE, MEGALITH, ATOM, BRICK, UNIT, Lego, STONE, Cstone, PLINTH, and CORNERSTONE are all building blocks. CINDER is a lightweight aggregate made from coal or volcanic ash, ADOBE is a type of sun-dried mud BRICK, MEGALITH is a large STONE used in prehistoric monuments, ATOM is the smallest particle of an element, BRICK is a rectangular block of clay or other material, UNIT is a single thing or person, Lego is a type of interlocking plastic BRICK, STONE is a hard natural material, Cstone is a type of concrete block, PLINTH is a base or support for a structure, and CORNERSTONE is a STONE at the corner of a building.