Don't let the volatility we've seen in recent days rattle you. Sure, quite a few stocks have pulled back. But for many of them, their underlying businesses are as strong as ever. The sell-off of these stocks presents an opportunity to buy at a lower price.

Which stocks are smart picks in the midst of market turbulence? Here are three unstoppable stocks to buy in October.

A smiling person holding a cup of coffee while looking at a laptop.

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1. Nvidia

It's easy to become distracted by the noise surrounding Nvidia (NVDA 0.35%) right now. Some are worried about how long the chip shortage will go on. Others are concerned about the possibility that Intel will recapture market share from Nvidia in the gaming market. 

All of this misses the big picture. Nvidia's long-term growth prospects remain outstanding. Even if the company surrendered some market share in gaming (which isn't a foregone conclusion), the market continues to expand enough for Nvidia to continue winning.

It's a similar story with the data center market. Nvidia's graphics processing units (GPUs) should enjoy robust demand for a long time to come in powering data center servers. That will be likely even if rivals become more competitive.

Increased adoption of artificial intelligence in apps and in self-driving cars presents massive growth opportunities for Nvidia. The emergence of the metaverse -- a 3D virtual universe that many predict will be the future of the internet -- should provide an even greater catalyst for the company. Nvidia is an unstoppable stock because it's poised to profit from these unstoppable trends.

2. Square

Speaking of unstoppable trends, the shift away from cash to digital payments is definitely one of them. And Square (SQ 16.13%) stands out as one of the top fintech stocks that are making this shift happen.

Square started out enabling small businesses to process credit card payments. Over the years, the company has built out a full-blown ecosystem supporting small to medium-sized businesses. Square has plenty of room to grow this seller ecosystem by offering new products and services, expanding internationally, and targeting larger customers.

Arguably the most important growth driver for Square's seller ecosystem in the future is that the company recently obtained a banking charter. But this charter is also critical for Square's other ecosystem targeting individuals -- Cash App. 

Cash App already enables users to transfer money to their friends, invest, prepare taxes, and more. It will soon allow customers to buy now and pay later thanks to Square's acquisition of AfterPay.

Look for Square to add banking services in the not-too-distant future. The company could disrupt traditional banking in a big way. In doing so, its stock seems likely to be a huge winner for investors over the next decade and beyond.

3. Vertex Pharmaceuticals

Vertex Pharmaceuticals (VRTX 0.78%) hasn't been a winner so far this year. The biotech stock is down more than 20%. However, Wall Street analysts think that Vertex could rebound in a major way. They have good reasons for this optimism.

Most importantly, Vertex's cystic fibrosis (CF) drugs still have plenty of room for sales growth. The company estimates that there are 83,000 individuals with CF in the U.S., Canada, Europe, and Australia. More than 30,000 of them could benefit from Vertex's CF drugs but aren't yet. 

Meanwhile, Vertex hopes to expand beyond CF. The company and its partner, CRISPR Therapeutics, hope to file for regulatory approvals of gene-editing therapy CTX001 in 2023 for treating rare blood diseases beta-thalassemia and sickle cell disease. Vertex expects to report key data this year from a phase 2 study of VX-147 in treating focal segmental glomerulosclerosis, a rare genetic kidney disease.

The big biotech is also targeting a couple of not-so-rare diseases. Vertex is evaluating VX-548 in phase 2 clinical studies as a treatment for acute pain. It's also testing gene therapy VX-880 in an early stage clinical study in treating type 1 diabetes. In addition, Vertex has a growing cash stockpile that it's likely to use in funding business development deals that bolster its pipeline.