Subject: How do we know what's in a black hole?

I was reading about black holes (again), and barely got past the 
description of them when a new question struck me.  If there's a certain 
limit from which even light can't escape (event horizon), how do we really 
know there's a singularity inside?  Since the gravity of the black hole 
bends space enough to prevent the escape of light, it must also prevent the 
escape of other forms of electromagnetic radiation, meaning none of our 
tools can detect what's in there, right?

Thanks,

Greg

Re: How do we know what's in a black hole?