By Louis Navellier of InvestorPlaceFour times a year we cross an invisible barrier. You definitely can't see it, but you can certainly feel the powerful change from it. I'm talking about earnings season. We've officially ended the first quarter and earnings announcements are right around the corner. I expect the S&P 500's operating earnings to be up almost 70% during the first quarter. Many lumbering blue-chip stocks will see modest growth as part of this trend, but small-cap stocks with explosive potential is where the real opportunity is for investors. Strong earnings are often rewarded with double-digit gains in just a few days after a great report -- so now is the time to buy into the best small-cap stocks before the earnings surge!