Caspases, a unique family of cysteine proteases, are involved in both the initiation and execution phase of cell apoptosis. They also play a vital role in the inflammatory responses. Caspases exist in cells as inactive zymogenes and undergo a cascade activation, which inevitably leads to the cell death. These highly specialized enzymes create the network of intracellular signaling through proteolysis. The network regulates the function and the life span of cells in physiological and pathological states.