
It was conjectured over 50 years ago that electrons in a high quality conductor could flow collectively as a viscous fluid, just like air or water. While impurities and umklapp scattering forbid this behavior in conventional metals, it has now become possible to study electrons that flow like classical fluids in high quality devices. I will focus on recent theoretical and experimental advances in understanding and observing hydrodynamic behavior of electrons in graphene. In particular, I will describe two experiments I have been involved in: (1) detecting a “hydrodynamic" enhancement of thermal conductivity in a (quasi)relativistic electron-hole plasma; (2) directly imaging of the breakdown of Ohm's law.