Subject: SMELLING: What Are Those Receptors Exactly ?

I have been trying to figure out smell for a few hours now. Just became 
curious in it. I realize there are volatile odours out there which float 
around and make there way up our nostril to waiting receptors. There are 
SO many odours out there, many I've never had the honor of whiffing before 
but of course the brain will receive this input and allow me to smell it.

I keep coming back to these receptors having some basic "elemental" shape 
which ALL odours can be broken down in to for us to be able to smell all 
odours in the world. 

Is this true? 

What are all these elemental receptor shapes?

Any good books to read?

Re: SMELLING: What Are Those Receptors Exactly ?