This chapter describes the basic physics underlying the newly emerging technique of electrospray deposition (ESD) as applied to biological macromolecules. Fabrication of protein films and microarrays are considered as the most important applications of this technology. All the major stages in the ESD process (solution electrification, formation of a cloud of charged microdroplets, transformation of microdroplets into ions and charged clusters, deposition, and neutralization) are discussed to reveal the physical processes involved, such as space charge effects, dissipation of energy upon landing and neutralization mechanisms. Fundamentals of ESD are presented together with a discussion of potential practical problems in realizing ESD through dielectric masks. Retention of structure and functional properties of protein molecules in ESD-fabricated films and microarrays is discussed in detail.