Citigroup is highlighting its services business, which handles money movement globally, as central to its corporate transformation at an investor day event. This segment is becoming an increasingly important driver of profits for Citi, accounting for almost half of total earnings last quarter. Analysts see this unit processing payments and moving funds between accounts as a "crown jewel" and "diamond in the rough" at the lagging financial institution. Investors will receive an in-depth presentation on the services division's operations and growth strategies from Citi leadership on Tuesday.