The inherently heterogeneous nature of nanoparticles (NPs) presents a significant challenge for fundamental studies into relationships between structure and reactivity. Utilizing analytical methodologies which probe individual NPs is a promising approach to overcoming this challenge. To this end, analytical methods which utilize correlated electroanalytical and optical measurements have been developed which enable detailed studies into the electrochemical reactivity of individual NPs. Scanning electrochemical cell microscopy (SECCM) is employed to directly measure the rate of electrochemical reactions at individual NPs, while optical spectroscopy is used to probe the structure of these particles in situ. This enables the correlation of electrochemical kinetic data with particular NP structures, providing valuable insights into structure-function relationships for a given electrochemical process. Additionally, in situ spectroscopic measurements facilitate investigations into the mechanisms responsible for transient changes in electrochemical reactivity (e.g., catalyst deactivation). Initial studies applying the described methods to model electrocatalytic systems will be presented.