Knowledge is getting increasingly more complex. Learners, from Kindergarten to higher education, require powerful tools to connect complex ideas. This paper explores the range of studies that investigated concept maps as learning, metacognitive, collaborative, and assessment tools to support integrating complex ideas. Research suggests that concept maps can be successfully implemented in a wide variety of settings, from K12 to higher and professional education. However, the effectiveness of concept maps depends on different factors, such as concept map training and choosing a suitable form of concept map to match the task and learner. Developing proficiency in concept mapping takes time and practice and should not be first introduced in higher education. Concept map training could start as early as Kindergarten and include concept map generation, interpretation, and revision. This paper concludes that, if implemented thoughtfully, concept maps can be versatile tools to support knowledge integration processes towards a deeper understanding of the relations and structures of complex ideas and facilitate life-long learning.