In the past 20 years, ETFs have become one of the most popular investment vehicles. They offer lowcost access to as set classes for investors. With over $1 trillion in assets under management, the ETF structure has become one of the fastest growing areas of the financial markets. There was one ETF in 1993 known as the SPDR (the S&P 500 Depository Receipt). Now there are over 2000 ETFs, representing many asset classes.