The state of children's fitness is the responsibility of all who are involved with children. As early childhood professionals, they have a duty to educate the whole (thinking, feeling, "moving") child. Moreover, teachers of preschoolers can be more realistic than parents in their assessment of children's physical inactivity levels, and preschool teachers' prompting of children has a positive influence on those levels. By ensuring that children stay active while in their care, early childhood professionals can help combat obesity and promote healthy lifestyles from the beginning. In this article, the author defines physical fitness in terms of health-related fitness and skill-related fitness, and describes its five components: (1) cardiovascular endurance; (2) muscular strength; (3) muscular endurance; (4) flexibility; and (5) body composition. She provides some movement suggestions for fitting physical activity into the daily curriculum and presents Active Start--Physical Activity Guidelines for Children Birth to Five Years.