Theoretical chronobiology of circadian timing-gold mine or minefield?

From noisy single cells to coupled tissues, circadian rhythms depend on interactions across multiple scales and on external time cues. Oscillator theory has played a central role in making sense of these dynamics, particularly in explaining synchronization and entrainment. Yet the same abstractions that make oscillator models powerful can also mask biologically relevant differences between systems. In this perspective, we outline where oscillator theory has been most informative, where it can mislead, and what this means for future experimental and theoretical work. While we focus here on circadian rhythms, related principles extend to other biological oscillators across timescales.