<prompt> Human: I am in early 40s and currently invest my IRA and 401K in Vanguard 500 Index Fund Admiral only. Is this a good idea in terms of maximizing growth minimizing risk? What would you do to make it better?  <response>: maximizing growth minimizing riskYou cant do both of these things at the same time; I think you meant you want to have a balance of growth with acceptable risk. We cant predict the future, but you could look at the annualized returns of various funds and also their standard deviation as a marker for their volatility. The target date retirement funds include mid-cap and small-cap sized companies, in proportion to their market value overall so the large-cap companies still make up a lions share of the stock, and they also include international and bond indexes. If you want to hold just one fund, you could increase the growth potential a little by using a total market fund instead of a 500 index fund.If you want to diversify into more than just US stocks, such as to include international and bond components, then a target date fund might do the trick. Comments that suggest focusing on a specific sector that the commenter feels will be hot in the upcoming future are pointing you in the direction of more risk increased volatility, and away from diversification which moderates volatility.You might want to do some reading on the theory of asset allocation -- there are books on the topic. 