SPARK (Simple Platform for Agent-based Representation of Knowledge) is a cross-platform, free software for multi-scale agent-based modeling (ABM). Specifically, it provides some unique features for biomedical model development at the systems level. Our goal is to provide a lightweight, convenient, extensible and computationally efficient platform for ABM modelers. SPARK is under continuous development by the team at CIRM at the University of Pittsburgh. For more information, including complied binary distribution, manual and documentation, please visit SPARK official website at www.pitt.edu/~cirm/spark