The idea of using software agents as fundamental building blocks within software systems has been a subject of relevant interest over the past three decades. This chapter seeks to contextualize the longstanding debate surrounding the role of software agents as building blocks of software systems within the framework of contemporary software development. Specifically, the focus of this chapter is on the programmatic dimension of development with the intent to emphasize the integration of cognitive agents as fine-grained modular units within software architectures. The metaphors that characterize cognitive agents are explored as promising means to enable the treatment of agents as effective building blocks of fine-grained software architectures. A relevant part of this chapter is dedicated to examine the implications of adopting cognitive agents within mainstream software development practice. Additionally, this chapter presents a preliminary proposal of a novel system level to use cognitive agents in the scope of contemporary software development.