An interface for the single-cell RNAseq-oriented loom format. Loom files are an HDF5-based format for storing and interacting with large single-cell RNAseq datasets. loomR provides an interface for working with loom files in a loom-specific way; we provide routines for validating loom files, iterating with chunks through data within the loom file, and provide a platform for other packages to build support for loom files.