Being able to think smells?

I have no idea whether or not this is a figment of my imagination.  However, I sometimes think that I can "think" smells. 

What I mean is, I might concentrate really hard on thinking about a particular smell, say cut grass for example, I can seemingly visualise the smell in my head. 

So rather than having some cut grass in front of me, I could concentrate hard and recollect inside my brain what it smells like. 

Is this just placebo?  My mind playing tricks with me?

Or can anybody else think of a smell and then visualise it in her head? 

(Not sure if I am making sense!)