The problem with serial repitching has beer makers and cell biologists scratching their heads. Clearly, something about the fermentation process is making new generations of yeast less able to ferment. But what? Heat shock response is a complex process because cells are capable of making 1000s of different proteins. But only a subset of these proteins are expressed at any one instant, and the subsets differ inside each organelle in the cell. So maintaining the function of these proteins—proteostasis—requires a complex signaling mechanism that switches on the relevant genes in each organelle. This switching process must be coordinated across the cell, since organelles depend on each other. The process of communication and coordination is called cross-organelle response, or CORE, and it is poorly understood. But this is an important emerging area of cell biology: biologists are beginning to realize that CORE plays a crucial role not just in heat shock response but in metabolism in general, and even in processes such as aging.

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