In a large pot, boil several quarts of water. Add green beans and boil for 5 minutes. Drain, and set aside.
Place a large skillet on medium heat. Add chopped bacon and cook for about 5 minutes. Drain any excess bacon drippings.
Add chopped onions and cook for another 5 minutes or until softened. Add garlic and cook for about 1 minute.
Add green beans and sauté for 10 minutes, stirring frequently.
Add balsamic vinegar, cover, and reduce heat to low, and cook for another 10 minutes. The balsamic vinegar will reduce, thicken and start to caramelize the vegetables. Add salt and freshly cracked black pepper to taste. Remove to a serving dish and enjoy!