Citigroup Inc. (NYSE: C) is truly a global bank.� With operations in more than 100 countries, it leads in consumer banking, credit cards, corporate lending, investment banking and brokerage.� But its forays into the U.S. mortgage market, and its huge exposure to the U.S. retail and corporate banking markets, created huge losses from which the company is still recovering.

Citi, guided by a prudent and savvy investment banker, Vikram Pandit, has embarked in one of the most ambitious and difficult transformations ever attempted by a financial institution.� It is shedding bad assets, cutting costs, raising capital and has segregated the impaired assets and businesses that Citi would like to dispose into a so-called "bad bank," a subsidiary by the name of Citi Holdings.� The success of the restructuring will depend on both Citigroup's execution and on the underlying strength of the U.S. and global economies.

But therein lies the huge upside.� As I have written before, there are few investment opportunities more profitable than the restructuring and turnaround of a business.� And given the huge size of Citi's balance sheet and the fact that banks are pro-cyclical to the economies in which they operate, the potential gains are extremely large.