<prompt> Human: Best way to let a hard earned 10K grow quickly? No debt, no car, 20k in roth, maxed out 401k 437; employee match, 5k in emergency savings. 40k salary job. currently single, no kidsnet gain of 500month after rent and food.probably wont be looking to buy a house soon realistically...  <response>: Assuming your 401k and Roth are invested in index funds as suggested by the sub, how much more riskreturn do you want?At the same risk level you should definitely max out the 401k. You can branch off into EM or smallcap ETFs for a little more risk with the benefit of diversification.Beyond that, picking individual stocks, sector specific ETFs or mutual funds, swingday trading, leveraged trading, FDs as suggested by someone else, going to a casino... 