  Software systems evolve over their lifetime. Changing conditions, such as
requirements or customer requests make it inevitable for developers to perform
adjustments to the underlying code base. Especially in the context of open
source software where everybody can contribute, requirements can change over
time and new user groups may be addressed. In particular, research software is
often not structured with a maintainable and extensible architecture. In
combination with obsolescent technologies, this is a challenging task for new
developers, especially, when students are involved.
  In this paper, we report on the modularization process and architecture of
our open source research project ExplorViz towards a microservice architecture.
The new architecture facilitates a collaborative development process for both
researchers and students. We describe the modularization measures and present
how we solved occurring issues and enhanced our development process.
Afterwards, we illustrate our modularization approach with our modernized,
extensible software system architecture and highlight the improved
collaborative development process. Finally, we present a proof-of-concept
implementation featuring several developed extensions in terms of architecture
and extensibility.
