The paper is, for the most part, a review, written in its original form for an International Workshop on Vortices, Superfluid Dynamics, and Quantum Turbulence, held in Lammi, Finland, in 2010. Achievements are reviewed, and a strong emphasis is placed on problems that are either unsolved or still the subject of active discussion. These problems often call for more powerful experimental techniques, including local probes and actual visualization of the turbulent motion. Special emphasis is placed on recent progress in the development of visualization.
- Quantum turbulence