The inner constitutes a remarkable biological detector that exhibits sensitivity at sub-nanometer levels, while exhibiting 6 orders of magnitude in its dynamic range. The detection process is performed by hair cells, which transduce incoming mechanical displacements into electrical signals. These cells are operant in a viscous medium, but can nevertheless sustain oscillations, amplify incoming signals, and even exhibit spontaneous motility, indicating the presence of an underlying active process that pumps energy into the system. Theoretical models have proposed that a hair cell constitutes a nonlinear system with an internal feedback mechanism that can drive it across the Hopf bifurcation and into an unstable regime. We will present latest results on the self-tuning in hair cells in response to external mechanical input. Secondly, we have developped techniques that allow us to track movements of multiple hair bundles in parallel. With extracellular coupling elements left intact, the hair cells exhibit a significant degree of phase-locking, over the relevant physiological range of stimulus. We demonstrate that this inter-cell coupling plays an important role in shaping the response of the system.