This episode is a tutorial lecture about original subject matter jurisdiction in federal courts. It introduces--and focuses exclusively on--the doctrines of federal question under 28 USC 1331 and diversity under 28 USC 1332. I do not cover class actions nor any of other (less common) bases for original subject matter jurisdiction. In this episode I also focus on a very practical application of the contemporary doctrine.  Consult other episodes for lectures about historical context and for the other bases for federal subject matter jurisdiction (esp. supplemental and removal jurisdiction).