This document summarizes information about big and small nuclear reactors. It discusses two big reactors, JET and ITER, noting their participants, energy production, and dates. It then discusses three small reactor designs: the Toshiba 4S reactor, the Hyperion reactor, and the Thorium reactor (SSTAR), providing details on their designers, operating lives, outputs, advantages, and applications. It notes that small reactors have advantages but also challenges related to costs.