MDCC Fluctuations

[bighomage]

I'm still really new to the stock market and trying to figure out some of the dynamics of the market. A stock I've been following, Molecular Devices (MDCC), has had an interesting last couple of days so I was wondering if anyone could explain to me what caused its fluctuations, so I can understand some of the market better.

Yesterday afternoon, it had a conference call to announce its 2nd quarter earnings. The revenue was a record high and a significant jump over the same quarter last year. For the day, the stock jumped (which makes sense to me) about 3.5%. However, on Yahoo! finance, it said last night that in after hours trading, the stock plummeted by about the same amount, placing its price at a slightly lower value than it had opened at that day. Sure enough, today it opened at about that price, wiping out all the gains from the day before.

So, I understand why the stock went up from the new articles I read, but can anyone look at the articles and explain to me why it went back down immediately? An explanation would be of immense help to me.