Rise to Power
After Caligula's father's death he lived in Rome, first with his mom, then with Augustus's wife, Livia, then with his grandmother. Then is 32, he joined Tiberius in his retirement on Capri.
Major Achievement while in Power
By the spring of 38 the character of Caligula's rule changed drastically. He got an illness that affected his mind.
Fall from Power or Death
When he returned back to Rome he lived in constant fear and danger of assassination. His fourth wife and daughter were murdered at the same time he was.
His being of mentally unstable.