Extention of stay is an application made by a non-immigrant visa holder to the U.S. Citizenship and Services Center (USCIS) when he/she wishes to stay in the US beyond the validity of his/her current non-immigrant visa. 

Generally, all non-immigrant visas are eligible for extension of stay except for certain types of non-immigrant visas i.e. K1, K2 visa etc...  To be eligible for extension, the non-immigrant visa must be valid at the time of filing and the applicant's passport must be valid throughout the whole application process.  However, in the event that your non-immigrant visa has already been expired, you may still file for an extention if you have sufficient proof to support your application.  Please contact Cipolla Law Group if you wish to file for an extension of your non-immigrant visa.