With the death of the pope, the tasks of organizing a papal election and overseeing the day-to-day needs of the church fall to Cardinal Eduardo Martinez Somalo.
The 78-year-old Spaniard has been "camerlengo" or chamberlain of the Holy Roman Church since 1993, although the job was basically just a title while Pope John Paul II was alive.
Now Cardinal Martinez's responsibilities range from ensuring that nothing is touched or tampered with in the papal apartments to selecting the technicians who will sweep the Sistine Chapel for electronic bugs, cameras and recording devices.
As chamberlain, Cardinal Martinez is the only person who may authorize the photographing of the pope's dead body, but only for documentary purposes and with the body dressed in pontifical vestments.
In the Vatican's employ since 1956, Cardinal Martinez worked under five popes. In February 2004 he retired as prefect of the Congregation for Institutes of Consecrated Life and Societies of Apostolic Life.
From 1979 until his appointment to the College of Cardinals in 1988, he was one of Pope John Paul's closest aides, serving as "sostituto," or assistant, secretary of state.
As chamberlain he took temporary charge of the church's affairs until a new pope is elected. His first duty was to certify the death of the pope.
According to rules set by Pope John Paul in 1996, Cardinal Martinez was to seal the pope's study and bedroom and take possession of the Apostolic Palace and papal palaces at St. John Lateran in Rome and at Castel Gandolfo, south of the city.
In consultation with senior cardinals, he makes the arrangements for the pope's funeral and sets the date for the beginning of the meetings necessary to prepare for the conclave.
The chamberlain -- together with Cardinal Angelo Sodano, Pope John Paul's secretary of state, and U.S. Cardinal Edmund C. Szoka, governor of Vatican City State -- is responsible for preparing the cardinals' rooms in the Vatican's Domus Sanctae Marthae guest house.
While the office of pope is vacant, the chamberlain presides over what are called "particular congregations of the cardinals." In addition to the chamberlain, the particular congregations include three cardinals chosen by lot. The chamberlain's assistants serve for three days, then are replaced by three other cardinals chosen by lot.
The group of four deals with "ordinary affairs" not requiring the discussion and consent of the entire College of Cardinals, which meets under the presidency of the college's dean, Cardinal Joseph Ratzinger.
The particular congregation is the only body empowered to decide whether a reason exists for anyone in the conclave to communicate with anyone outside the gathering.
Cardinal Martinez and his three cardinal assistants also are responsible for giving approval to the individuals chosen to serve as priest-confessors, doctors and domestic staff for the cardinals in the conclave.
The chamberlain, with two masters of ceremonies, is responsible for administering an oath of secrecy to the non-cardinals whose service is needed by the conclave.
Under Pope John Paul's 1996 rules, Cardinal Martinez is required to write up a report on the results of each ballot, place it in a sealed envelope and give it to the new pope after he is elected.
If after about 30 ballots, one papal candidate has not received two-thirds of the votes, the chamberlain presides over the discussion of whether or not the cardinals want to move to a simple majority vote.
Although his role in the preparation and work of the conclave is key, the chamberlain's duties end inside the Sistine Chapel with the election of a new pope.