The ability to measure protein half-lives on a large scale in human cells should contribute to our understanding of a variety of physiological and pathological processes. To meet this goal, Eden et al. (see the Perspective by Plotkin) developed a method called bleach-chase. Bleach-chase was used to reveal an unexpectedly simple response of fluorescently tagged protein half-lives to stresses and to drugs that stop cell division: Long-lived proteins become longer-lived. It appears that changes in cell growth cause changes in the intracellular dilution rates of proteins, which are not balanced by corresponding changes in active protein degradation.