What happened

On Thursday, shares of electric-car maker Tesla (TSLA 1.44%) continued to rebound from their worst one-day sell-off on record earlier this week. The stock jumped as much as 8.9%, but as of 11:15 a.m. EDT today, it had settled to about a 6% gain.

The move higher on Thursday extends Wednesday's rally for the growth stock. Based on this two-day rebound, investors seem to believe that Tesla shares were oversold during a big sell-off on Tuesday, creating a buying opportunity.

Model X interior

Tesla Model X. Image source: The Motley Fool.

So what

Until Wednesday, Tesla was seeing significant selling pressure this month. The stock appeared to be taking a breather after a wild run higher. It had gained about 500% between the end of 2019 and Aug. 31 -- a move that seemed to persuade some shareholders that it was time to do some profit-taking.

But after the September sell-off worsened on Tuesday, when the stock slid about 21% in a single day, some investors appear to be aggressively buying shares.

Now what

While Tesla is still down 19% in September, investors should keep in mind that the growth stock certainly isn't cheap. The company trades at about 17 times sales, up from a multiple of about eight as recently as a few months ago and a multiple of three just last year. With the stock's valuation changing so quickly, continued volatility is almost inevitable.