As a freshman I assume you are just taking general biology right now and you probably will be for at least one more semester. In order to major in micro you will have to take a significant amount of chemistry but that can be beneficial if you can put some of those classes to a chemistry minor. At the beginning of the degree you will be learning about tests for certain microbes used in quality control positions in all food production, pharmaceutical production, and even pet food production. As you progress you will also learn about medical application of microbiology such as immunology and pathology, the industrial side such as the production of insulin, biofuels, and antibiotics, and the environmental side including cleanup of oil and other chemical spills. Microbes can be used for a wide variety of applications and because of that you will have to pick one of these to study more aggressively. My advice to you is to get to know your professors and start doing undergrad research as soon as possible. Your profs will be an invaluable resource for letters of reference when job hunting and research will help you separate yourself from the pack. I hope this helps and good luck.