With this Special Issue "History of Energy Technologies and Lessons for the Future" edited by Seth C. Rasmussen, Substantia contributes to the celebrations of the 150^th anniversary of the periodic table.

Cover image: Darkfield, Polarized Light micrograph (magnification 200x) from Pleurosigma (marine diatoms), by Michael J. Stringer, Westcliff-on-Sea, Essex, United Kingdom. Courtesy of Nikon Small World (1^st Place, 2008 Photomicrography Competition, https://www.nikonsmallworld.com).