difficult, complicated problems are theoretically solvable with additional resources, specialized expertise, analytical, reductionist, simplification, decomposition techniques, scenario planning, and following good practices. Complex are characterized by unknown unknowns, and emergence. Patterns could be uncovered, but they are not obvious. A complex system can be described by Euclid’s statement that the whole is more than the sum of its parts. Really complex projects, a.k.a. very complex, or chaotic: characterized by unknowables. No patterns are discernible in really complex projects. Causes and effects are unclear even in retrospect. Paraphrasing Aristotle, a really complex system is different from the sum of its parts. By applying the discovery in measuring work complexity described in Requisite Organization and Stratified Systems Theory, Elliott Jaques classifies projects and project work (stages, tasks) into seven basic levels of project complexity based on such criteria as time-span of discretion and complexity of a project's output: Level 1 Project – improve the direct output of an activity (quantity, quality, time) within a business process with a targeted completion time up to 3 months. Level 2 Project – develop and improve compliance to a business process with a targeted completion time of 3 months to 1 year. Level 3 Project – develop, change, and improve a business process with a targeted completion time of 1 to 2 years. Level 4 Project – develop, change, and improve a functional system with a targeted completion time of 2 to 5 years. Level 5 Project – develop, change, and improve a group of functional systems/business functions with a targeted completion time of 5 to 10 years. Level 6 Project – develop, change, and improve a whole single value chain of a company with targeted completion time from 10 to 20 years. Level 7 Project – develop, change, and improve multiple value chains of a company with target completion time from 20 to 50 years. Benefits from measuring Project Complexity are to improve project people feasibility by matching the level of a project's complexity with an effective targeted completion time, with the respective capability level of the project manager and of the project members. Positive, appropriate (requisite), and negative complexity Similarly with the Law of requisite variety and The law of requisite complexity, project complexity is sometimes required in order for the project to reach its objectives, and sometimes it has beneficial outcomes. Based on the effects of complexity, Stefan Morcov proposed its classification as