This introduction to the molecular biology of the cell envisions cytology and physiology from an experimental point-of-view, to understand the structure and functions of animal cells. Nervous impulse transmission, muscular contraction, and cellular electrophysiology are considered to illustrate cell specialization and its impact on the cell structures and the functions that exist in living systems. Cellular processes that are of interest to the engineers will permit to introduce the sensors and devices used to observe and measure biological systems, including through microscopy.