Nite (Knight Equity) was purchased by Citi group in 2004, and Auto ( Automated Trading Desk) was purchased by Citi in 2007.
They are both trading execution and order management units, which create markets. "We help our clients grow their businesses. Our systems can take a large client order, break it up into many smaller components, and then execute that order more efficiently and effectively." Basically, they are selling the company's shares to the public in a way that it won't create a bubble nor disrupt the trading system, but create a platform for growth. Like building a pyramid for the company.