The late-time behavior of solutions to the wave equation on Kerr spacetime is governed by inverse polynomial decay. However, at earlier time-scales, numerical simulations are found to be dominated by quasinormal modes (QNMs). These are exponentially damped oscillatory solutions with complex frequencies characteristic of the system. In this talk, I will present a rigorous characterization of QNMs for the scalar wave equation on Kerr. They are obtained as the discrete set of poles of the meromorphically continued cutoff resolvent. The construction combines the method of complex scaling near asymptotically flat infinity with microlocal methods near the black hole horizon. I will also discuss the distribution of QNMs in both the high and low energy regimes. In particular, I will present uniform low energy resolvent estimates, which exclude the accumulation of QNMs at zero energy