Atlas of Wood Pellet Components features compilation of over 300 photographs taken between 2019 and 2021 while the authors (Agnieszka Drobniak, Zbigniew Jelonek, Maria Mastalerz and Iwona Jelonek) were developing methodology of using reflected light microscopy in identification of pellet fuels constituents. These photomicrograps provide documentation of the composition of wood pellets and demonstrate the array of impurities that can be present. As such, this atlas is a valuable source of information for anyone interested in pellet fuels, optical microscopy, and quality assessment techniques. See the atlas introductory text and component classification at: Drobniak, A., Jelonek, Z., Mastalerz, M., Jelonek, I., 2021, Atlas of Wood Pellet Components: Indiana Geological and Water Survey, Indiana Journal of Earth Sciences, v. 3, https://doi.org/10.14434/ijes.v3i1.31905.