There are many pieces of advice saying essentially the same thing. Some go as far back as 23 B.C., when the Roman poet Horace wrote carpe diem -- an exhortation to seize the day.

Similarly, in his 2009 letter to shareholders, Warren Buffett wrote, "When it's raining gold, reach for a bucket, not a thimble."

In both cases, the lesson is to take advantage of opportunities when they present themselves. With the S&P 500 falling nearly 25% over the past year and recently down some 11% from its 52-week high, that's an opportunity. Lots of terrific stocks are on sale.

Here are three growth stocks to learn more about and consider adding to your portfolio. (And note that when a growth stock falls far enough, it can become a value stock.)

1. MercadoLibre

MercadoLibre (MELI -1.00%), with a recent market value near $50 billion, operates a massive online marketplace in Argentina, Brazil, Mexico, Colombia, Chile, Venezuela, Peru, and many other Latin American countries. There are close to twice as many people in Latin America as in the U.S.

Many have likened it to Amazon and eBay. And just as eBay used to be home to PayPal Holdings, MercadoLibre has Mercado Pago, a digital payment platform, operating in Brazil, Argentina, Mexico, Colombia, Chile, Peru, and beyond. So this growth stock offers investors exposure to the e-commerce and fintech spaces.

In the company's impressive second quarter, revenue popped 56.5% over year-earlier levels on a currency-neutral basis, while total payment volume surged 83.9% and gross merchandise volume advanced 26.2%.

MercadoLibre's stock was recently more than 53% below its 52-week high, and its price-to-earnings (P/E) ratio, while not exactly low at 208 recently, was still way below its five-year average of 766. 

2. Netflix

Netflix (NFLX -0.20%) has for many years been a poster child for growth stocks, doubling its investors' money over and over. Its ride has been bumpy, though, and a big bump occurred after it posted its first-quarter results, featuring shrinkage in its number of subscribers and the expectation of more of the same. That sent its stock south by some 35% in a single day. More recently, shares were off around 65% from their 52-week high.

Investors are divided about Netflix. Bears worry about growing competition, and the fact that the company has spent so much on buying and creating content that its price increases are driving subscribers away.

Bulls, on the other hand, see losses stabilizing, a promising ad-supported pricing tier, and a rosy future. In the company's second quarter, revenue grew by 8.6% year over year, with management noting that a strengthening dollar abroad is providing a headwind.

It's too early to count Netflix out. It has more than 220 million paying subscribers in almost 200 countries, showing that it's still a popular service. The stock's P/E ratio was recently 22, well below its five-year average of 110.

3. Microsoft

The market value of Microsoft (MSFT -1.05%) recently topped $2 trillion, and it employs more than 200,000 people, nearly half of them abroad. It encompasses many solid businesses, too, such as the ubiquitous Windows computer operating system and the Microsoft 365 suite of productivity software, including Word, Excel, Outlook, among other applications.

The company also owns the Azure cloud-computing platform, Surface devices, Xbox gaming systems, Skype, and LinkedIn. Investors should be happy to see the company shifting some of its products, like Office and Xbox, to a subscription model that delivers fairly reliable recurring income.

It's a dividend-paying stock. The recent yield of 0.85% might not seem impressive, but it has been growing by about 10% annually on average over the past five years.

Despite the company's massive size, Microsoft itself is also growing. Fourth-quarter revenue was up 12% (16% in constant currency), with its Azure and Other Cloud Services segment popping 40% (46% in constant currency).

Microsoft's shares were recently down 18% from their 52-week high, and the P/E was 30, below its five-year average of 37, suggesting the shares are undervalued.

These three stocks are well worth considering for your long-term portfolio.