  In this contribution to the proceedings of the 29th Solvay Conference on
Physics I will give an overview of some key challenges in our theoretical
understanding of the rheology of glasses, focussing on (i) steady shear flow
curves and their relation to the glass and jamming transitions, (ii) ductile
versus brittle yielding in shear startup and (iii) yielding under oscillatory
shear. I will also briefly discuss connections to the reversible-irreversible
and random organization transitions as well as to the broad field of memory
formation in materials.
