Execution chamber at San Quentin State Prison in California.

Photo courtesy California Department of Corrections

For thousands of years, many governments have punished people convicted of certain crimes by putting them to death, using various means to accomplish this. The death penalty is considered by many to be the ultimate form of punishment for those who have committed society's most heinous crimes, including rape and murder. As times have changed, so have the methods of execution.

The idea of someone being put to death is not a pleasant one. About 54 of the world's countries and 35 American states have a death penalty [source: Amnesty International]. The vast majority of executions in 2009 took place in China, Iran, Iraq and Saudi Arabia [source: Amnesty International].

The form by which prisoners are executed is changing. In America and a growing number of other countries, lethal injection has become the most commonly used form of capital punishment, replacing other forms such as hanging and the electric chair. In this article, we'll examine how lethal injection is carried out and what a prisoner experiences in the days prior to execution.