I will discuss the concept of AGN X-ray `states' and how they relate to 
states in X-ray binary systems. I will then discuss the timing similarities 
between AGN and binary systems and what they reveal about the structure of 
the X-ray emission region and the origin of the variability. Time permitting 
I will talk about the relationship between the X-ray variability and 
variability in other wavebands, particularly the optical.