Markets fall as well as rise and you may not get back all that you invest. Some markets are more volatile than others. E.g. cash and money market type funds have lower volatility but lower growth potential whereas higher risk areas such as emerging markets and China can go up or down +/-50% and even more in just 1 year. Whilst you may be investing for the medium long (5yrs +) or the longer term (10 yrs +), in the short term 1, 2, 3 yrs etc, higher risk funds could fall dramatically. How much could you afford/tolerate your investment falling in value in the short term for your investment to then recover and target medium and longer term growth.