The visa stamped in your passport at the U.S. Embassy or Consulate is for permission to enter the United States for a specific purpose and period of time.  Students are usually given an F-1 visa. Spouses and children of F-1 visa holders are assigned an F-2 visa.  Since this stamp is only important for entry and re-entry to the United States, there is no need to worry if it expires while you are here if you are maintaining your student status.  If you need to leave the U.S. temporarily and your visa has expired, a DSO will counsel you on how to obtain a new visa.  You will need to notify the Student Development Office at least one week in advance of your departure to allow time to prepare the necessary paperwork. Because a visa is only a permit to apply for entry into a country, it is not possible to obtain a U.S. visa while you are in the U.S. To apply for a visa, you must go to a U.S. Consulate or Embassy in a country other than the United States, usually your home country.