Mastering any physical skill, be it performing a pirouette, playing an instrument, or throwing a baseball, takes practice. Practice is the repetition of an action with the goal of improvement, and it helps us perform with more ease, speed, and confidence. So what does practice do in our brains to make us better at things? Our brains have two kinds  of neural tissue: grey matter and white matter. The grey matter processes information in the brain, directing signals and sensory stimuli to nerve cells, while white matter is mostly made up of fatty tissue and nerve fibers. In order for our bodies to move, information needs to travel from the brain's grey matter, down the spinal cord, through a chain of nerve fibers called axons to our muscles. So how does practice or repetition affect the inner workings of our brains? The axons that exist in the white matter are wrapped with a fatty substance called myelin. And it's this myelin covering, or sheath, that seems to change with practice. Myelin is similar to insulation on electrical cables. It prevents energy loss from electrical signals that the brain uses, moving them more efficiently along neural pathways. Some recent studies in mice suggest that the repetition of a physical motion increases the layers of myelin sheath that insulates the axons. And the more layers, the greater the insulation around the axon chains, forming a sort of superhighway for information connecting your brain to your muscles. So while many athletes and performers attribute their successes  to muscle memory, muscles themselves  don't really have memory. Rather, it may be the myelination of neural pathways that gives these athletes  and performers their edge with faster and more efficient  neural pathways. There are many theories that attempt to quantify the number of hours, days, and even years of practice that it takes to master a skill. While we don't yet have a magic number, we do know that mastery isn't simply about the amount of hours of practice. It's also the quality and effectiveness of that practice. Effective practice is consistent, intensely focused, and targets content or weaknesses that lie at the edge  of one's current abilities. So if effective practice is the key, how can we get the most  out of our practice time? Try these tips. Focus on the task at hand. Minimize potential distractions by turning off the computer or TV and putting your cell phone  on airplane mode. In one study, researchers observed 260 students studying. On average, those students were able to stay  on task for only six minutes at a time. Laptops, smartphones,  and particularly Facebook were the root of most distractions. Start out slowly or in slow-motion. Coordination is built with repetitions, whether correct or incorrect. If you gradually increase the speed of the quality repetitons, you have a better chance  of doing them correctly. Next, frequent repetitions with allotted breaks are common practice habits of elite performers. Studies have shown that many top athletes, musicians, and dancers spend 50-60 hours per week on activities related to their craft. Many divide their time  used for effective practice into multiple daily practice sessions of limited duration. And finally, practice in your brain in vivid detail. It's a bit surprising, but a number of studies suggest that once a physical motion  has been established, it can be reinforced  just by imagining it. In one study, 144 basketball players were divided into two groups. Group A physically practiced  one-handed free throws while Group B only  mentally practiced them. When they were tested at the end of the two week experiment, the intermediate and experienced players in both groups had improved by nearly the same amount. As scientists get closer to unraveling the secrets of our brains, our understanding of effective practice will only improve. In the meantime, effective practice is the best way we have of pushing our individual limits, achieving new heights, and maximizing our potential.