Here at Zacks, we focus on our proven ranking system, which places an emphasis on earnings estimates and estimate revisions, to find winning stocks. But we also understand that investors develop their own strategies, so we are constantly looking at the latest trends in value, growth, and momentum to find strong companies for our readers.Of these, value investing is easily one of the most popular ways to find great stocks in any market environment. Value investors use tried-and-true metrics and fundamental analysis to find companies that they believe are undervalued at their current share price levels.On top of the Zacks Rank, investors can also look at our innovative Style Scores system to find stocks with specific traits. For example, value investors will want to focus on the "Value" category. Stocks with high Zacks Ranks and "A" grades for Value will be some of the highest-quality value stocks on the market today.Trinseo (TSE) is a stock many investors are watching right now. TSE is currently sporting a Zacks Rank of #2 (Buy) and an A for Value.Value investors also frequently use the P/S ratio. This metric is found by dividing a stock's price with the company's revenue. This is a popular metric because sales are harder to manipulate on an income statement, so they are often considered a better performance indicator. TSE has a P/S ratio of 0.51. This compares to its industry's average P/S of 0.64.Finally, investors will want to recognize that TSE has a P/CF ratio of 3.94. This metric focuses on a firm's operating cash flow and is often used to find stocks that are undervalued based on the strength of their cash outlook. This company's current P/CF looks solid when compared to its industry's average P/CF of 6.26. TSE's P/CF has been as high as 346.19 and as low as 3.77, with a median of 14.71, all within the past year.These figures are just a handful of the metrics value investors tend to look at, but they help show that Trinseo is likely being undervalued right now. Considering this, as well as the strength of its earnings outlook, TSE feels like a great value stock at the moment. Zacks' Top Picks to Cash in on Artificial Intelligence In 2021, this world-changing technology is projected to generate $327.5 billion in revenue. Now Shark Tank star and billionaire investor Mark Cuban says AI will create "the world's first trillionaires." Zacks' urgent special report reveals 3 AI picks investors need to know about today.See 3 Artificial Intelligence Stocks With Extreme Upside Potential>>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Trinseo S.A. (TSE): Free Stock Analysis Report To read this article on Zacks.com click here.