Rise to Power
In 32 A.D. Caligula joined Tiberius in his retirement on Capri. During 33 A.D. Drusus, who was Caligula's brother had died and Caligula was next in line. When Tiberius died Caligula was acclaimed emperor in March.
Major Achievements While in Power
In Caligula's first months of reign he gave legacies that were left from Tiberius and Livia to the people in Rome. Then later on he adopted his cousin Tiberius Gemellus as his son and heir.
Fall From Power or Death
When Caligula returned to Rome, he was in constant and fear and in danger of assassination. He got murdered by a Praetorian Gaurd. His only daughter and forth wife were murdered at the exact same time on January 24th A.D.
His being mentally unstable.