<prompt> Human: I understand the tremendous power of compound interest and am curious what kind of investments have compound returns. Thanks  <response>: Just about any profitable investment pays compound interest. You earn interest the first time, and then the next time youre earning interest on the previously earned interest. This is compounding.So where to invest depends on your goals. If its for retirement, contribute to a 401K or open a Roth IRA and invest in low expense ratio index funds. 