Warren Buffett and his company Berkshire Hathaway (BRK.A -1.12%) (BRK.B -0.86%) are widely known as some of the greatest investors of all time, with a strong track record for beating the broader market. Buffett has also been known to say that he's not the biggest fan of diversification because he believes it's a protection against ignorance.

The team at Berkshire Hathaway certainly practices what Buffett preaches and keeps its nearly $324 billion equities portfolio heavily concentrated in just a handful of assets. In fact, roughly 74% Berkshire's portfolio is invested in one high-growth stock and one ultra-safe asset.

The high-growth stock

If you follow Berkshire and Buffett, then it will come as no surprise to hear that the consumer tech giant Apple (AAPL 0.01%) is the largest stock in Berkshire's equities portfolio, currently accounting for more than 41%. Berkshire first bought Apple in 2016 and now owns over 911.3 million shares valued at more than $133.7 billion.

One of the reasons Buffett has gone all-in on Apple is because the company has created one of the strongest brands in the world, which, if you look through Berkshire's portfolio, is definitely one trait the Oracle of Omaha seems to really look for when evaluating stocks.

In fact, as legend has it, one of the main reasons Buffett first started looking more closely at Apple is after a member of Berkshire's board of directors lost his iPhone. "I felt like I lost a piece of my soul," David Gottesman supposedly said at the time.

Strong brands can carry companies through a variety of difficult economic situations. People are still likely to buy the iPhone, for instance, during high levels of inflation or a recession because the device plays such a critical role in their lives. So, during times of inflation like we're in now, Apple can pass on higher costs associated with running its business to its customers without too much pushback.

Apple also happens to be a cash cow, having generated more than $28 billion of operating cash flow and a profit surpassing $25 billion in its most recent quarter. The company has also repurchased more than $467 billion of stock over the last decade, something we also know Buffett -- or any investor, for that matter -- absolutely loves.

The ultra-safe asset

It should come as no surprise to Buffett fans that the asset I am referring to here is not a stock, but rather cold, hard cash. That's right -- almost 33% of Berkshire's portfolio is straight cash.

Under Buffett's leadership, Berkshire's equities portfolio keeps a minimum of $30 billion in cash and cash equivalents. At one point last year, that cash pile was up close to an astonishing $150 billion.

Now, a lot of people question this strategy. Why not put that cash to work, given earning a little something on this amount of money can go a long way? But Buffett has long maintained a large hoard of cash to prepare for economic shocks and investing opportunities. When the pandemic hit, I am sure Berkshire shareholders slept easier at night knowing that the company had heaps of cash on hand to stomach a range of adverse economic scenarios.

Having this amount of cash also allows Buffett and Berkshire to move quickly when they come across good investing opportunities. That might mean repurchasing shares of Berkshire, acquiring a company, reinvesting in the business, or investing in stocks. In the first three months of the year, Buffett and Berkshire put $51 billion of that cash to work.