This seems like a silly question, but I have not been able to find the answer.  How do I get the username from the lastmodifiedbyid on custom objects?  I've queried the user object, but it does not understand the relationship with 'user'.

This seems like a silly question, but I have not been able to find the answer.  How do I get the username from the lastmodifiedbyid on custom objects?  I've queried the user object, but it does not understand the relationship with 'user'.