Here's the scientific secret behind perfect coffee

“Variables such as temperature, water chemistry, particle size distribution, water to coffee ratio, time, and, perhaps most importantly, the quality of the green coffee all play a key role in producing a great tasting cup, and it is our control over these variables that makes the cup reproducible,” he wrote.
 The concentration of coffee syrup is a key factor in making your coffee experience enjoyable. These are the natural chemicals found in coffee grounds. The ideal concentration of coffee syrup is 1.2-1.5%, which can be achieved through certain brewing methods, specifically "pour over, Turkish, Arabica, Aeropress, French press, syphon or batch brewing."
 Water also plays a key role in the whole process, and knowing the composition of your tap water can make a difference (use this database to learn more about tap water).
 “Brewing water with low levels of calcium ions and bicarbonate (HCO₃⁻) — i.e. soft water — will result in a highly acidic cup, sometimes described as a sour cup. Brewing water with high levels of HCO₃⁻ — typically hard water — will produce a chalky cup because the bicarbonate neutralizes most of the flavor acids in the coffee.”
 The ideal acidity is right in the middle, and a good way to collect the flavors of a good cup is to brew a batch with Evian, which has "one of the highest concentrations of bicarbonate in bottled water." The texture of the coffee is also important, but Hendon details that there's debate over both coarse coffees (small particles with negative flavors are less likely to affect the flavor) and fine coffees (more likely to have richer, bolder flavors), so it's best to experiment and find what you like best.
 Finally, freshness is incredibly key. The longer the bean sits in its husk, the more "volatiles," gaseous organic molecules that affect flavor, escape. The coffee you buy at a café is usually freshly roasted, rarely more than four weeks from the roast date. So, as a rule of thumb, buy it fresh, and use it quickly.