A Non-Correlated Portfolio:   True Portfolio Diversification 

Many Investment Professionals recommend investors invest in stocks, bonds, mutual funds as well as holdings with stocks of companies in different countries, and many will call this diversification.

The Modern Portfolio Theory says that the risk of any investment can be reduced and/or performance increased by forming a portfolio of diverse and non-correlated assets

Simply put: a truly diversified portfolio contains not only a range of  different asset types, but also assets that have low correlation to one another.

Thus a portfolio comprised of only stocks, bonds and mutual funds may not be enough to provide true diversification.

Most Investment Professionals and investors do a good job of identifying the most  basic needs for  different investments within the traditional markets; they don't always succeed in reducing the risk that their assets will move in tandem.