Libraries that are a foundation of the Avogadro 2 project. Avogadro 2 is a chemical editor and visualization application, it is also a set of reusable software libraries written in C++ using principles of modularity for maximum reuse. The development of the first generation Avogadro application and library is documented in our paper, and this remains the preferred method of citation at present. The motivation for rewriting Avogadro, along with improvements and changes made in Avogadro 2 are summarized in our Source article. We provide a set of permissively licensed, open source, cross platform software components in the Avogadro 2 libraries, along with an end-user application with full source code, and binaries. The library features updated and improved rendering, where we built upon the abstraction provided by previous API, but implemented a simple scene graph. This makes use of features such as impostor sphere rendering, resulting in significant rendering speed improvements while improving the quality of the visualization. The core is built for scalability, looking to enable the analysis of larger chemical structures and simulations being produced by computational chemistry codes today. Emphasis has also been placed on making it even easier to extend, using simple Python scripts to add simulation input capabilities, and data input/output along with access to full-blown C++ plugin APIs where more control is required. WWW: https://www.openchemistry.org/projects/avogadro2/