What happened

Shares of Materialise NV (MTLS 3.98%), a Belgian provider of 3-D printing software and services, rocked the stock market today when its shares plunged more than 25% in early trading then recovered half their losses. (The stock's still down 13.3% as of 1:30 p.m. EST.)

So what

Why did this happen? It's impossible to say. So far, the company hasn't announced any news that might explain the plunge -- nor indeed commented on the stock's sudden volatility. There have been no upgrades or downgrades announced on Wall Street either -- analysts haven't so much as changed a single price target so far as I can tell.

What we do know is that 9:57 a.m. this morning, the stock's dramatic decline freaked out someone at Nasdaq, which halted trading of Materialise shares. Ten minutes later, trading was allowed to resume, and the shares slowly regained some of their losses.

Glowing red arrow on graph trending down.

Materialise stock plummeted today -- for no reason anyone can fathom. Image source: Getty Images.

Now what

Barring management commenting on the sudden volatility, investors may have to wait until earnings come out to get a clue what it was, exactly, that so spooked Materialise shareholders today. Fortunately, the wait probably won't be long. Materialise last reported earnings on Oct. 31. Add three months to that, and the next quarterly report should be due out sometime at the end of this month.

As of today, analysts aren't expecting any huge surprises. Earnings should be flat against last year's Q4 -- $0.05 per share. Sales should be up a modest 10% at $56.1 million. When the news comes out, we'll see how close Materialise came to those marks.

Check out all our earnings call transcripts.