This paper introduces DREAM.3D, an open-source software environment designed for processing, segmenting, quantifying, representing, and manipulating digital microstructure data. The authors discuss the challenges in integrating existing software tools to create a scalable and expandable codebase, focusing on data structure, storage, ease of use, intellectual property, and long-term maintainability. DREAM.3D aims to standardize the format of material microstructure data and facilitate collaboration among researchers, government labs, and industry. The software uses a geometric mesh element construct to hold digital microstructure data, a hierarchical grouping for feature and ensemble representation, and a scalable layout for information storage. The pipeline concept allows users to design workflows visually, ensuring data availability and error detection. DREAM.3D also supports plugin architecture for future algorithm additions and integration with other software packages like ParaView for visualization. Case studies demonstrate the software's capabilities in reconstructing, segmenting, and statistically analyzing polycrystalline metal datasets, as well as generating synthetic microstructures. The authors conclude that DREAM.3D reduces the time and cost of microstructural characterization by leveraging community developments and integrating disjointed research areas.This paper introduces DREAM.3D, an open-source software environment designed for processing, segmenting, quantifying, representing, and manipulating digital microstructure data. The authors discuss the challenges in integrating existing software tools to create a scalable and expandable codebase, focusing on data structure, storage, ease of use, intellectual property, and long-term maintainability. DREAM.3D aims to standardize the format of material microstructure data and facilitate collaboration among researchers, government labs, and industry. The software uses a geometric mesh element construct to hold digital microstructure data, a hierarchical grouping for feature and ensemble representation, and a scalable layout for information storage. The pipeline concept allows users to design workflows visually, ensuring data availability and error detection. DREAM.3D also supports plugin architecture for future algorithm additions and integration with other software packages like ParaView for visualization. Case studies demonstrate the software's capabilities in reconstructing, segmenting, and statistically analyzing polycrystalline metal datasets, as well as generating synthetic microstructures. The authors conclude that DREAM.3D reduces the time and cost of microstructural characterization by leveraging community developments and integrating disjointed research areas.