If you have been married for less than two years when you receive Permanent Residence based upon marriage to a US citizen, your status will be conditional.  Conditional Permanent Residence is valid for two years.  If your green card has an expiration date two years from the date it was issued, you are a Conditional Permanent Resident.

 

As a Conditional Permanent Resident, you must apply to remove the conditions before the expiration of those two years.  If you do not do so, your Permanent Resident status will end and you will be removeable from the United States.

 

If the marriage is still intact, the USCIS expects that the couple will file a joint petition to remove the conditions.  This is a similar process to the initial Permanent Residence application.  The couple will submit documentary evidence of their marriage and will attend another interview with USCIS. 

 

If the marriage ends before the two year mark, the Permanent Resident spouse can apply alone to remove the conditions.  The Permanent Resident must prove that the marriage ended (usually a death or divorce certificate) and must also show that the marriage was genuine before it ended.  This can be difficult.