I am an applied mathematician who studies biological clocks, particularly the mammalian circadian clock. We have daily rhythms, entrained by light-dark cycles, that are regulated by a central clock in our brains, the suprachiasmatic nucleus (SCN). Oscillations with periods of 24 hours are generated in the SCN via transcriptional-translational negative feedback loops involving core clock genes. I study these feedback loops and the resulting behavioral rhythms by creating and analyzing differential equations models. I also study the oscillations recorded in experiments by applying wavelet-based time series analysis and other methods, with the goal of gaining insight about the underlying mechanisms that generate the oscillations.