Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of metrology systems specialist Nova Measuring Instruments (NASDAQ:NVMI) sank 10% today after President and CEO Gabi Seligsohn announced that he is stepping down.

So what: The stock has skyrocketed over the past five years under Seligsohn's leadership, so his decision to step down raises some uncertainty over Nova's potential going forward. Specifically, Seligsohn transformed Nova from a single-product OEM company to a multiproduct solutions provider, fueling impressive top- and bottom-line growth in the process.

Now what: Nova said that Executive Vice President Eitan Oppenhaim will be promoted to become president and CEO, effective July 31. "I am delighted that the Board has decided to accept my recommendation that Eitan take my place at the helm," said Seligsohn in a statement. "Our company is performing extremely well; we have an excellent seasoned management team, leading edge systems and technology and, most importantly, we have wonderful people across the entire organization." With the stock now off its 52-week highs and trading at a forward P/E of 12, Fools might even want to use today's pullback to buy into those positives.  

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