Though building an investment portfolio around a base of core holdings is not new, making it happen in an uncomplicated fashion is a rather recent development.
Here are ETFs in five major asset categories that are very much worth looking at and adding to every investment portfolio for the diversity of exposure and other advantages they potentially bring to investors.
1) ASSET CLASS: U.S. Stocks
FUND: Schwab U.S. Broad Market ETF (SCHB)
This $1.3 billion fund is an excellent choice for advisors and investors that want a core domestic stock ETF. Well-known equity ETFs like the SPDR S&P 500 (SPY) and SPDR Dow Jones Industrial Average ETF (DIA) are still good, but they're limited to owning large company stocks.
In contrast, SCHB tracks the 2,500-stock Dow Jones U.S. Broad Stock Market Index. This particular benchmark automatically includes exposure to not just large cap stocks like Google and Coca-Cola, but faster growing mid- and small cap stocks too. Annual portfolio turnover is just 5% and annual expenses are a meager 0.04%. The fund carries a dividend yield of 2.02%. And here's one other benefit: Schwab brokerage customers can trade SCHB commission free.
2) ASSET CLASS: Inflation Linked Securities
iShares Global Inflation Linked Bond Fund (GTIP)
If there's one thing we've learned from Europe's financial crisis, it's that concentrated exposure to a single bond issuer is a big risk. This basic truth applies in Europe and anywhere else throughout the globe.
GTIP offers bond investors an opportunity to hedge against higher inflation while simultaneously diversifying both credit and currency risk.
The fund holds sovereign debt that is publicly issued and denominated in the issuer's own domestic market and currency.
While many ETF investors know about U.S. Treasury Inflation Protected Securities (TIPS), too few understand that diversifying both credit and currency risk away from the U.S. government is an absolute must.
The top three countries that GTIP's bonds own are the United States (34.98%), United Kingdom (20.49%), and Brazil (11.96%).
The fund tracks the BofA Merrill Lynch Diversified Inflation Linked Bond Index. GTIP charges annual expenses of 0.40%.
3) ASSET CLASS: Commodities
FUND: Greenhaven Continuous Commodity Index Fund (GCC)
4) ASSET CLASS: Global Real Estate 
5) ASSET CLASS: Emerging Market Stocks
