Warren Buffett is one of the best investors of our time, so it's little surprise that investors would want to know as much as possible about Buffett's portfolio. And while there's plenty to know about it, I think there's one little talked-about aspect that's important to take note of.

That aspect is this: Warren Buffett loves financial stocks. Loves them. And that may be surprising to many investors since financial stocks -- and bank stocks in particular -- haven't been the subject of too many favorable headlines in recent years.

I do need to point out that when I talk about Warren Buffett's portfolio, I'm actually referring to Berkshire Hathaway's (NYSE:BRK-A)(NYSE:BRK-B) portfolio. Warren Buffett is far and away the largest shareholder of Berkshire Hathaway, he's the architect of the Berkshire Hathaway that we know and love today, and he makes most of the company's major investment decisions. So I think it's fair to refer to it as "Warren Buffett's portfolio."

With that out of the way, when we look at Buffett's portfolio, we find no fewer than five financial stocks among the top ten holdings. The California banking giant Wells Fargo (NYSE:WFC) holds the top spot in the portfolio, while credit card powerhouse American Express (NYSE:AXP) is in the number three spot. German insurer MunichRe, U.S. Bancorp (NYSE:USB), and Goldman Sachs (NYSE:GS) round out the group.

Dig through the rest of Buffett's portfolio and you'll find that trend persisting. Tally up all of Berkshire's major stock holdings and you'll find that darn near half of the $100 billion-plus portfolio is in financial stocks.

Source: S&P Capital IQ.

Notably, this tally only includes Berkshire Hathaway's common-stock ownership, which means that it doesn't reflect the company's multi-billion dollar preferred-stock stake in Bank of America (NYSE:BAC).

I think there are two lessons here. The first is that widely held opinion doesn't make something so. If that were the case, financial and bank stocks would indeed be uninvestable following the financial crisis. But if we think Warren Buffett knows a thing or two about investing -- and I think that's a reasonable conclusion -- and we look at Warren Buffett's portfolio, then it's obvious that financial stocks are far from uninvestable.

The second lesson involves the "why" of Warren Buffett's portfolio being so overloaded with financial stocks. The takeaway isn't simply that you have to be investing in banks and insurance companies right now. Though I think there's a good case to be made that that's true, a big part of the reason that Buffett's portfolio is so chock-full of financial companies is that this is a sector that he understands well. And so the takeaway for us is not "buy financials" but rather "buy what you understand."