Three main factors are required to promote muscle growth:   1.  Muscular stimulus. Resistance training (weight training) is needed to make the muscles work, use energy and cause microscopic damage to the muscle fibers.   2.  Nutrition - after intense exercise the muscles need to replenish their stores of fuel.   3.  Rest - it is during the rest or recovery phase that the muscles repair the microscopic damage and grow.Here are the supplements I'd recommend for Muscle-building.Creatine:A great supplement that always produces positive health and muscle-building benefits. Helps to fill the muscles with fluid making you stronger and able to lift heavier and recover faster. Good bodyweight gains achieved with this, which allows you to lift more for better muscle growth stimulation.Protein Powders:Whey protein isolate is the best fast acting protein to aid in repair and growth of muscle tissue after an intense training session. Casein Protein is a slow digesting protein best taken just before bed to supply the body with a continuous flow of amino acids for repair and growth through the night while you sleep.Muscle size increases due to hypertrophic adaptation and an increase in the cross section area of individual muscle fibers. Intensive exercise impacts more on the strength influencing fast twitch type II fibers, therefore the increase in muscle size is accompanied by greater strength.Some other muscle building supplements include various amino acids, protein bars, growth hormone, and a huge selection of multi vitamins, all with varying ingredients used to help promote muscle growth. Growth hormone is released by the pituitary gland and is responsible for our growth, particularly during our teenage years when we hit puberty. In time, this hormone slows down, but by if we supplement with it, we can see a large increase in growth in both muscles and sometimes in bone growth as well. This is a popular choice for muscle building supplements, since the results are very stunning and often surprise people with repeated use. Protein bars are a safe and delicious way to help promote muscle growth. Many people love to eat them in order to help stave off hunger and provide the body with an extra boost of energy, without sugar or fat. Protein bars are made by hundreds of different companies, so you should be able to find one you like with a few different tries. How to increase muscle size.We must train hard enough to damage the muscle fibres so our body rebuilds them bigger and stronger.We can trigger this type of muscle growth by using:   1. Heavy weights.   2. Low repetitions (6-8).   3. Long rest periods (2-4 mins).The low reps affect muscle fibres in a unique way that causes maximum muscle growth. The heavier the weight, the more muscle fibres are used.This type of training also stimulates our natural levels of testosterone. Testosterone is the 'muscle growth' hormone!I prefer doing compound exercises for this type of training like the squat, the bench press and the shoulder press. You can use a lot of weight in these movements to strongly stimulate muscle growth.A study published in 1997 found that knocking out the myostatin gene in mice enabled them to grow bigger muscles. Studies on cattle also found that those that were naturally bulky produced less myostatin protein. The scientists believe these latest findings show that the same process works in humans.They also believe that techniques used to block this gene in mice could be used on humans, including those who have difficulty developing muscles."This is the first evidence that myostatin regulates muscle mass in people as it does in other animals," said Dr Se-Jin Lee, professor of molecular biology and genetics.