Genetic modification begins in a laboratory where scientists change the genetic makeup of plants and then test them for the desired traits. Following successful laboratory tests, they must pass a series of approval processes to reach the market. They must first receive approval to be field-tested. Following approval and successful field tests, they must receive approval to be marketed. When marketing approval is granted, the seeds are mass produced and sold to farmers who will plant, harvest and sell them as commodities in the food supply market. In the United States, regulation of GMOs is divided between the USDA, EPA and FDA. The USDA conducts a mandatory review of genetically modified plants to detect if they will affect the environment and if they are safe to grow. The EPA conducts a mandatory review of GM plants that are insect resistant or herbicide tolerant to assess whether or not they will impact the environment. Finally, the FDA conducts a voluntary review to assess whether the GM plants are safe to eat. All GMOs currently on the market have gone through this process.