Model exchange and re-use has been greatly enhanced over the last decade by the emergence of standard model exchange languages such as SBML and CellML. Model design and re-use becomes even more tractable with modularity: larger, more complex models can be built using well-understood smaller models. CellML has long been modular, and SBML now has a modularity 'package' which allows modular model construction. We will present an overview of the capabilities of the modeling standards and tools that facilitate modular modeling. (http://antimony.sf.net).