Just like the ugly duckling, exchange traded funds (ETFs) were once an oddity floating in a pool of the more popular mutual funds. But their success has grown beautifully and gracefully, like a swan.

At the start of the decade, ETFs were a curiosity for most investors. Today, many financial advisors find them indispensable, as they are more transparent and less expensive than their predecessors, reports David Hoffman for Investment News. The biggest plus is that ETFs can be traded throughout the day, unlike mutual funds which do so only at the close.

Through these advantages, the ETFs have swanned into 629 strong, with $608.42 in assets  by the end of 2007, according to the Investment Company Institute.

State Street Global Advisors started it all, with the SPDRs. The growth continued throughout the industry, spreading to heavyweights such as Barclays, PowerShares, and Vanguard.

What is the next ten years going to look like? We predict big, exciting things from the ETF industry as they attract more investors and continue their innovations.