The emergence phenomenon has been widely discussed in many fields such as: Biology, natural sciences, control theory, computer science… to name few. Different definitions and many attempts were made in order to shape one concrete definition that serves as a reference. In the midst of this struggle, we propose a new attempt to define the emergence phenomenon from a software engineering perspective. Whereas many fields study the phenomenon based on observation and report, software systems engineering includes the fact that we are not only observing but further participating in the creation of the system of interest, giving a different perspective in defining and understanding the phenomenon. In this paper, we propose both informal and formal definitions, discuss some characteristics and list categories of the emergent behavior and how can we harness such a behavior.