When Elsa von Frühlingfeld presented her invention to King Frederick Augustus II of Saxony, people thought it was a hoax. She used the recently isolated element uranium to heat a pot of water and used the steam to power an engine, keeping the uranium active through a process she called "atomization." Her device, the Nucleum, ushered in a new era of energy and prosperity for decades to come.

Saxony grew from a small regional power to the center of European science and technology. Now, a generation later, factories are still hungry for more energy and demand bigger and more Nucleums to be built, more uranium is imported from the nearby country of Bohemia, and railways and power lines are built throughout the country to tame the power of the atoms to the great cities of Saxony. Inventors, engineers and industrialists flock to the Saxon court and compete to become the leader in this new industrial revolution.

Nucleum is a complex board game in which players take on the role of industrialists trying to succeed during the economic and technological boom of 19th-century Saxony, powered by the invention and spread of the Nucleum (a nuclear reactor).

Players earn victory points by developing their networks, building and powering urban buildings, securing contracts and completing milestones. Each player will also receive unique asymmetric technologies, granting them special powers when unlocked. The flow of the game is continuous; players take turns taking actions without rounds or phases.