Cyclic steam stimulation (CSS) is an enhanced oil recovery technique used to extract heavy oil from underground reservoirs. The process involves injecting steam into the well to heat the oil, reducing its viscosity and making it easier to flow. After a period of steam injection, the well is allowed to produce oil, which can be collected for processing. This method is particularly effective in areas with thick, viscous oil, such as those found in the Athabasca Oil Sands in Canada. CSS can improve oil recovery rates and is often used in conjunction with other techniques to maximize production efficiency.