I will discuss a theoretical description of dynamical heterogeneities in glass-forming liquids, based on the premise that relaxation occurs via local rearrangements coupled by elasticity. In this framework, the growth of the dynamical correlation length and of the correlation volume are controlled by a zero-temperature fixed point. I will discuss a connection between this critical behavior to the properties of the distribution of local energy barriers at zero temperature. This description makes a direct connection between dynamical heterogeneities and avalanche-type relaxation, allowing us to relate the size distribution of heterogeneities to their time evolution. Within an avalanche, a local region relaxes multiple times, the more the larger is the avalanche. This property, related to the nature of the zero-temperature fixed point, directly leads to decoupling of particle di↵usion and relaxation time (the so-called Stokes-Einstein violation). This is joint work with Ali Tahaei, Giulio Biroli, Misaki Ozawa and Marko Popovic. In a second part of this talk, I will discuss how this concept of thermal avalanches applies more broadly. I will discuss the creep flow of amorphous materials and that of crumpled paper sheets. This is joint work with Daniel Korchinski, Dor Shohat and Yoav Lahini.