STEM (Science, Technology, Engineering, and Mathematics) education is a 21st century learning approach that is extremely important to students and children nowadays. Many developed countries have emphasized this approach to early childhood education (ECE). Although there are some challenges in promoting children's cognitive development in preschool, there are some best practices that early childhood educators can use as a guideline in planning, implementing, and evaluating their development at school. Four databases were used to find the best practices consist of Scopus, ERIC, Web of Science, and Science Direct. These databases are consulted to analyze published articles that produce findings on the best practices and challenges of implementing STEM activities that have been recorded either in kindergarten or preschool environments. The findings revealed there were 23 themes for the best practices and 10 themes for challenges that were successfully analyzed. In order to ensure that STEM education can be implemented with better quality in the future, educators should know the best way to implement the activities by practicing the best practices. In addition, educators also need to take action wisely when there are challenges in implementing STEM activities so that children can acquire meaningful experience when participating in the activities.