Human development is dynamic, multi linear, and highly plastic in nature. There are many factors that affect its progress. Theoretical perspective has contributed to the exploration of the study of personality and behaviour. Each developmental stages are marked with physical milestones that a human body should achieve. Cognitive and intellectual milestones are achieved through the right balance between biological and environmental influences. As explored in this module, if the balance is disturbed, there are numerous developmental challenges which might need to be dealt with.