At the dawn of the 19th century, an American-born Bavarian noble named Benjamin Thompson became interested in the subject of heat. Thompson, or Count von Rumford as his Bavarian patron titled him, wanted to know how heat could transfer through various media. He wrote extensively upon the subject, citing experiments such as plunging cored, peeled apples first into ice water, and then into boiling water to see how long it took for them to change temperature.
Many of his experiments focused on food -- the count was very much interested in the subject. His inventions include devices as the double boiler and a kitchen range.
Thompson also noted that if food were sealed within a vacuum and then submerged in heated, circulating water, it would cook.His musings upon the subject remained in semi-obscurity for nearly two centuries. But in the 1960s, chefs in America and France rediscovered the technique. Today, we call it sous-vide, which is French for "under vacuum." It's a popular -- though often time-consuming -- way to prepare food to exacting standards.
The basic concept is simple: Vacuum seal the food you wish to cook in plastic bags. Immerse those bags in a hot-water bath -- temperatures tend to range between 105 to 160 degrees Fahrenheit (40.6 to 71.1 degrees Celsius). Maintain the temperature of the bath for as long as the food requires to cook through, which can be up to 72 hours for some foods [source: ThermoWorks].
Maintaining the temperature precisely is critical. That's where immersion circulators come in. They're devices that circulate the water and regulate its heat so that your sous-vide dish comes out perfectly.