Cells across the tree of life respond to a sudden, nonlethal rise in temperature--heat shock--in similar ways. Following heat shock, proteins and mRNAs form clumps, certain genes turn on, and protein synthesis and cell growth sharply decline. The standard interpretation of these long-studied phenomena has held that thermal energy causes proteins to misfold, forming toxic aggregates that require cleanup by the induced chaperone proteins. Substantial challenges to this misfolding-catastrophe interpretation have remained. A fundamentally different picture emerges from recent work: aggregation instead reflects evolved, adaptive biomolecular condensation processes integral to the sensing of temperature, and chaperones regulate these condensed states. I will discuss molecular and physiological evidence for this alternative perspective, and its implications for a wide range of stress responses and environmental sensing problems.