Thinking in Systems Level 4 Hierarchy of Systems Thinking Slides (Google Slides)Thinking Slides (PDF) Systems may interact with other systems; they may have sub-systems and be a part of larger complex systems.TERMSSystem interactions - Complex systems - consisting of many different and connected partsSub-systems - a self-contained system within a larger systemSTANDARDSMS-LS1-3 / MS-ESS1-2