Thinking Routine

Parts, Purposes, Complexities

A simple, three-pass way to help students really look at how something is built.

What the routine does

Parts, Purposes, Complexities is a three-pass routine for slowing down and looking closely at something: what it's made of, why each piece is there, and where it gets tricky or interesting. It works on almost anything with structure: a machine, a paragraph, a policy, a piece of code, or a finished student paper.

It's especially handy anywhere students tend to stop at a surface impression ("this is a good essay" or "this program works") and you want to nudge them toward actually explaining how the thing works.

The three moves

A gentle facilitation tip

Keep the first pass purely descriptive. Students tend to want to jump straight to evaluating ("this part is weak") before they've actually named what's there. Hold Parts to naming and inventory only, and save the judgment calls for Complexities.

Using it for reverse engineering

I've used this routine with you for reverse engineering: handing you a finished, working example, like a literature review or a well-formatted paragraph, and asking you to figure out how it was made, rather than starting from a blank page.

How the pass shifts for reverse engineering
Parts
Take the finished piece apart into its components (paragraphs, sections, code blocks, design elements) the way you would with any object.
Purposes
Instead of just naming what each part does, infer the rule or decision behind it: what did the author have to know or decide to write it this way?
Complexities
Look for the places where the model makes a non-obvious choice, one your own first draft is likely to miss or get wrong.

The result works like a recipe pulled from a finished dish: you walk away with a concrete list of moves to try in your own work, drawn from a real example instead of an abstract instruction sheet. In each case, you already had a finished piece of writing in front of you and needed to see the structure underneath it, rather than being told the rules cold.

When to reach for this routine

Adapting it across grade levels

The three moves stay the same at every age; what changes is the object you hand students and how much scaffolding surrounds each move.

Elementary school
Try it on
A LEGO build, a classroom job chart, a paper airplane, or a recipe for no-bake cookies. Put the actual object in students' hands; don't describe it to them.
Parts
Say "pieces," not "parts." Have students point and name: "Show me one piece. What do you call it?" Chart their answers on sticky notes stuck directly to the object or a photo of it.
Purposes
Ask "what job does this piece have?" and require a sentence frame: "The ___ helps because ___." Reject "I don't know" as an answer; ask "what's your best guess?" instead.
Complexities
Ask one question only: "What would happen if we took this piece away?" Act it out or test it if you can (remove a LEGO piece and see what falls). Don't ask for an explanation beyond "it would fall" or "it wouldn't work right."
Middle school
Try it on
A well-built five-paragraph essay, a Rube Goldberg video, a persuasive ad, or a science lab's procedure section.
Parts
Require specificity, not categories. Reject "the beginning" and push for "the first two sentences, before the example starts."
Purposes
Ban the word "purpose" from answers. Force a why-question instead: "Why did the writer put this example here and not somewhere else?" If a student can't answer, have them try moving the part and predict what breaks.
Complexities
Have students find one part that is doing two jobs at once (a topic sentence that also transitions, a character who is both funny and suspicious). That double-duty is the complexity, not a vague "it's complicated."
High school
Try it on
A published op-ed, a literature review, a working codebase, a policy memo, or a piece of legislation, exactly the kind of finished, real-world artifact you've used with your own students.
Parts
Require students to name parts at the level of a craft move, not a content category: not "the argument section" but "the paragraph that pre-empts the counterargument before making the claim."
Purposes
Demand a decision, not a description: "What did the author have to decide, and what else could they have chosen instead?" A student who can't name the road not taken hasn't actually done this step.
Complexities
Push students to name a real trade-off the author made under a constraint (word count, audience, deadline, legal risk) and argue whether it paid off. This is where reverse engineering becomes evaluation, not just description.
A note for future teachers

Don't water the routine down for younger students by cutting a step; keep all three moves and shrink the object and the vocabulary instead. If a student's answer to Purposes or Complexities could apply to almost anything ("it's important," "it's complicated"), that's the sign to push harder for specifics, at any grade level.

Evidence base

Parts, Purposes, Complexities was developed by Harvard Graduate School of Education's Project Zero, the research center behind the Visible Thinking framework. It was built specifically for looking at complex systems, and is documented as part of Project Zero's Agency by Design research on maker-centered learning.

Its grounding is practitioner-facing classroom research rather than a controlled trial: Project Zero develops routines in classrooms with teachers, documents how they change student talk and work, and publishes the findings alongside the routine itself.

Primary sources

Background reading

Framing it for a syllabus or lesson plan

If you need language for a lesson plan or accreditation document, it's accurate to describe this as a research-based routine from Harvard's Project Zero, developed and refined through classroom-based research on visible thinking and maker-centered learning, rather than as validated by a peer-reviewed experimental study.