Have you ever stared at a blank screen, stuck, unable to move forward with your model?
You have a clear idea, but—just like writer’s block—your model refuses to take shape. It lingers in the back of your mind, stubbornly refusing to emerge, no matter how much you try.
You change angles, shift perspectives, dig up more data, reread your research—and still, nothing.
You even call for help. But time is running out.
I’ve been there. Many times. Especially when working on something completely new, something I’ve never modeled before (which happens quite often).
But over the years, I’ve found a lifeline—a hidden toolkit that has saved me countless times.
Let me introduce you to System Dynamics Molecules.
A Modeler’s Secret Weapon: System Dynamics Molecules
Years ago, iSee Systems, the company behind Stella Architect, introduced a powerful resource in collaboration with Dr. Jim Hines: a collection of predefined model structures designed to help system dynamics practitioners overcome creative roadblocks.
These modeling patterns, developed and refined by generations of modelers, are like building blocks—ready-made structures that you can copy, paste, and modify to fit your needs.
Some of these molecules have lost their original attribution over time, but their value remains—serving as essential tools for modelers facing challenges.
Many of these structures trace back to Jay W. Forrester’s pioneering work in Industrial Dynamics, while others were developed by renowned system thinkers such as John Sterman, Bob Eberlein, Peter Senge, and more.
You can explore the full library of structures at sdmolecules.org, where you'll also find acknowledgments for the thinkers behind these tools.
What Are System Dynamics Molecules?
System Dynamics Molecules are tested, reusable model structures that have been proven to work in real-world applications.
Instead of reinventing the wheel, you can use these pre-built components as starting points, allowing you to focus on refining your model instead of getting stuck at square one.
To make things even easier, Jim Hines provides:
✅ Clear documentation on how each molecule works
✅ A Stella model file with ready-to-use structures
✅ A simple copy-paste approach to jumpstart your modeling process
No more staring at a blank screen—just plug in a molecule and start building.
A Library of Solutions for Any System Dynamics Challenge
The System Dynamics Molecules collection is extensive, covering over 80 structures that can help tackle a wide range of modeling scenarios. Some of the key categories include:
✔ Aging Chains – Useful for workforce modeling, population dynamics, and product lifecycles
✔ Quality & Productivity Models – Representing efficiency, defects, and improvement processes
✔ Compound Interest & Exponential Growth – Capturing feedback loops in financial and environmental models
✔ Dimensionless Functions – Handling variables that scale dynamically across different scenarios
✔ And much more!
Each molecule comes with a full page of documentation that includes:
🔹 A stock and flow diagram to visualize its structure
🔹 The types of problems it solves
🔹 The underlying equations
🔹 A description of its function
🔹 The expected system behavior
🔹 Classic examples of where it has been applied
🔹 Potential pitfalls and limitations
🔹 Technical notes for implementation in modeling software
Think of it as a shortcut to a well-structured model—a set of battle-tested formulas that can help you move forward faster.
Get Started with System Dynamics Molecules
Instead of struggling with modeler’s block, why not explore this powerful set of modeling patterns?
🔹 Try Stella Online – Experiment with the molecules in your browser
🔹 Download the Stella Model – Get the full set for offline use (requires Stella)
For an even deeper dive, check out this presentation from iSee Systems, where Dr. Jim Hines himself introduces System Dynamics Molecules and explains how they can revolutionize your modeling workflow:
Would you like a step-by-step tutorial on how to use some of these molecules?
Let me know in the comments which structures you’d like to see in action, and I’ll create a video walkthrough to help you get started! 🚀
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