Competent cells are those that have had their cell walls altered to render it easier to incorporate foreign DNA into their interiors. Cells are made competent by a process that uses calcium chloride and heat shock, and cells that are undergoing very rapid growth are made competent more easily than cells in other stages of growth. Factors such as transformation efficiency, genetic markers, and packaging formats will impact the time and effort required for your project, and so too its success. Choose from a number of cell types and formats to ensure optimal function.