I agree with Angie - he's totally intimidated. I mean, stock clerk vs. phD scientist? Not usually a matchup you see. That's NOT to discourage you at all, but I will bet that *he* is discouraged, and prolly thinks that a smart person like you would never go for a "loser" like him or someone with a menial job. So definitely ask him out, and try not to talk about your work too much unless he asks - but don't say anything like "oh you wouldn't be interested in my boring old work" or he'll think you think that he won't understand it. Just be yourself. Have fun!..

He may feel intimidated by what seems like ur "brainy" job vs. his...
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If u like him, ask him for coffee, flirt with him, let him see the great girl u are, difuse some of his preconceived notions of what he thinks a "Ph.D Scientist" ... see if there's any chemistry lol. ..
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Angie..
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I'm the yin to Carlos' yang .....

That's weird that he won't look you in the eye anymore. Maybe he is insecure. Maybe he thinks you're smarter than him. Or, maybe he's a freakshow who doesn't believe in science -- and thereby felt he can no longer look at you, much less talk to you...
Sigh...
But a lot of guys don't care if a girl is more educated than he is...
It's a little weird that it took you 2 years to realize he was cute and that you might want to talk to him. I think you shouldn't really worry about why he's no longer talking to you. I might leave it alone. I mean, you weren't even friends with this guy. He was just someone at the grocery store. Maybe he had a dream that you were someone else, and when he realized you aren't a waitress/librarian/playmate/fill-in-fantasy here, he walked away...
Let him be. Find someone who isn't scared of your doctorate. You'll probably have more to say to each other...

I was gonna say the saaaame thing, but the other gals got to it first. He's intimidated. Maybe you can start up a convo with him about something non-intimidating that you are into. But I'm thinking he might not be confident enough to date you. It's still worth a try, but I'd be wary around guys with confidence problems. He might decide he's not good enough and break it off...