The Biology Dynamics Modeller BioDynamo is an open source, agent-based, simulation software that was originally designed to simulate the behaviour of billions of cells. Agent-based modelling (ABM) is a powerful methodology for studying complex systems in biology, epidemiology, economics, social sciences, medicine and more. BioDynaMo is a software platform to easily create, run, and visualise 3D agent-based simulations. BioDynamo allows users to reuse, adapt, or create modules that represents a specific biological behavior or entity. The core of the platform is written in C++ and is highly optimized to harness the computational power of modern hardware.