Turbulence is unique in its appeal across physics, mathematics and engineering. And yet a microscopic theory, starting from the basic equations of hydrodynamics, still eludes us. In the last decade or so, new directions at the interface of physics and mathematics have emerged, which strengthens the hope of ‘solving’ one of the oldest problems in the natural sciences. This two-part theme issue unites these new directions on a common platform emphasizing the underlying complementarity of the physicists’ and the mathematicians’ approaches to a remarkably challenging problem. This article is part of the theme issue ‘Scaling the turbulence edifice (part 1)’.