Research shows that outdoor play is essential to child development because it contributes to their cognitive, physical, social, and emotional well-being. Outdoor play isn't just fun, it's essential to help children keep physically fit and healthy. They improve their motor skills and learn about reflexes and movement control. Muscle strength and bone density is improved, along with heart and lung functioning. In turn, this can reduce possibilities of obesity and diabetes. Another benefit of free play is a child's emotional growth, and research shows that through play children build self-confidence. For example, by taking risks presented by physical challenges they see themselves to be successful at something and develop a sense of accomplishment. Free play allows children to experiment with different emotions. They often invent imagined situations; they can create and explore a new world. This allows them to fully express their emotions; they don't need to hold back. And they can learn to confront things which are scary. This often takes the form of releasing emotions from traumatic situations. They can 'play out' their traumas, sharing their feelings. Social interaction is another benefit and group play teaches children about social and cultural norms.