The culture of sedation and immobilization in the pediatric intensive care unit (PICU) is associated with PICU-acquired weakness, delirium, and poor functional, neurocognitive and psychosocial outcomes. A structured approach to introducing physical activity, as early as possible after PICU admission, may prevent these complications and optimize the holistic outcomes of critically ill children. Changing culture and introducing new clinical practice in PICU is complex, but can be approached systematically, using a "nuts and bolts" approach targeting the basic, practical considerations and essential required elements or components. Extending the construction analogy, this article reviews the relevant literature to describe the essential elements required to build and sustain a successful and safe early mobility program in the PICU.Effective early mobilization requires individual patient assessment and goal setting, using a collaborative inter-disciplinary, patient-and family-centered approach, to ensure mobility goals and physical activities are appropriate for the patient's age, condition/s, premorbid function, strength, endurance and developmental level. Early mobility activities for the pediatric age spectrum include active or active-assisted range of motion exercises, neurodevelopmental play, use of mobility devices, in-bed exercises, transfers, sitting or standing tolerance, crawling, pre-gait activities, ambulation and activities of daily living, with a focus on play as function. Although there are few complete contraindications to early mobilization, appropriate precautions and preparation should be taken to mitigate potential safety concerns. Although there are many perceived barriers to early mobilization in the PICU, at the level of patient, provider, institution and knowledge translation; these are not objectively associated with increased risk during mobilization and can be overcome through an engaged process of practice change by all members of the interprofessional clinical team. Early mobility programs could be initiated in PICU as systematic quality improvement initiatives, with established processes to optimize structural, process and system elements and to provide continual feedback, measurement, benchmarking and collaboration; to ultimately impact on measurable patient outcomes. Early, graded, and individually prescribed mobilization should be considered as part of the standard PICU "package of care" for all critically ill and injured children, in order to improve their functional status and quality of life after PICU discharge.