The beginning of this chapter motivates TES bolometers by juxtaposing them with competing technologies, specifically HEMTS and NTD bolometers, in order to highlight the deficiencies that TESs avoid. We discuss the principle of electrothermal feedback and derive stability criteria and sensitivity equations. Finally, we describe how the bolometers in this thesis were fabricated as well as the electronics used to read them. Throughout the chapter, we show data from dark measurements of our bolometers demonstrating acceptable transition temperatures, saturation powers, and time constants. We describe the cryogenic dewar used for these measurements in detail in Chapter 6.