Software development is a dynamic process where demands for change have been recognized to be inevitable. All forms of modifications to the user requirements cause software to change. The sources of changes could vary considerably and come from the users, business, technology, and organizations. Changes to requirements give rise to an intrinsic volatility, which is claimed to impact on many aspects of software development. Requirements Volatility (RV) is claimed to be a major source of risk to the management of software projects. Investigating the sources of, reasons for, and impacts of requirements changes is an important prerequisite for understanding the characteristics of requirements volatility. In this talk, I will discuss the nature of requirements changes and describe the results of our longitudinal study of requirements volatility. The results of this study have improved our understanding of this complex and multifaceted phenomenon and have provided valuable empirical evidence for the impacts of RV resulting in important insights for more effective management of requirements.