Turbulent mixing is a source of paradigm problems in physics, engineering and mathematics. Beyond this important interdisciplinary role, it has immense consequences for a broad range of applications in astrophysics, geophysics, climate and large-scale energy systems. In two volumes, we summarize and provide a perspective on the topic through some 20 articles focusing on turbulent mixing and beyond. The volumes are grouped, somewhat loosely, into those associated with fundamental aspects of turbulence and those specific to Rayleigh-Taylor turbulent mixing.