How complexity science can inform scale-up and spread in health care: Understanding the role of self-organization in variation across local contexts

► A complexity science perspective of scale-up and spread initiatives enables new insights about health care improvement. ► Self-organization is inherent in complex systems and it impacts the success rate of scale-up and spread efforts in health care. ► Relationships and sensemaking in health care settings influence self-organization in scale-up and spread initiatives. ► Scale-up and spread initiatives should encourage local adaptation of intervention designs to fit diverse care settings.