This book gives a detailed account on the electrochemical techniques to study the electrochemistry of particulate materials when the latter are immobilized on an electrode surface. Further, it is shown that very similarly the electrochemistry of immobilized droplets of solutions and liquids that are immiscible with the electrolyte solution can be accessed. Such measurements provide information on the electrochemistry of compounds, esp. organics, that are insoluble in water but soluble in organic liquids. Additionally, these measurements allow the determination of the Gibbs energies of transfer of cations and anions, and thus allow assessing the hydrobicity of ions, what is of great importance for pharmaceutical applications, biological studies and for many fields of chemistry. This book gives for the first time a comprehensive overview on the electrochemistry of particles and droplets immobilized on electrodes, as it was developed during the last 12 years.