Protein powder is widely used for muscle growth, but there are important things to know when it comes to its optimal use. Firstly, it should be taken within 30 minutes of completing a workout to maximize protein synthesis. Secondly, it's recommended to consume 20-25 grams of protein powder per serving to effectively stimulate muscle growth. Thirdly, it's best to mix protein powder with water rather than milk, as milk can slow down digestion. Lastly, protein powder should be used as a supplement to a balanced diet and regular exercise routine, rather than a replacement for whole foods.