Quarks are fundamental particles in the Standard Model of particle physics. They make up the protons and neutrons that we are familiar with, but also a zoo of other more exotic particle systems like pions and kaons. Quarks have never been isolated; they always form groups of two or three. But what are the rules that govern these quarks systems? Find out more with the quark puzzle, a set of 3D printable pieces that represent quarks. Each piece is labelled with a quark type, electric charge and colour charge, and has joints that allow it to connect to other quark pieces. Your students can use these to discover the rules of the strong interaction and colour charge, or to build your own models of particle systems. The 2D version of this puzzle was originally proposed b y Gettrust, E. (2010). Suggestions for educators The learning objectives of the activities we propose are: Resulting electric charges of particle systems are always integer numbers (e.g. -1, 0, +1) Resulting color charges of particle systems are always color neutral For baryons this means, for example, that a green quark must be combined with a red quark and a blue quark, and an antigreen quark must be combined with an antired and an antiblue quark. For mesons this means, for example, that a green quark must be paired with an antigreen antiquark. For younger students, we propose an activity with a high level of scaffolding guided by our scaffolded student worksheet. We also offer a teacher manual, which includes solutions. Introduction to puzzle pieces and combinations of 2 or 3 pieces Activity 1 - building a proton: combinations of colour charges and sum of electric charges Activity 2 - building an anti-proton: combinations of anti-colour charge and sum of electric charges Activity 3 - building neutrons and anti-neutrons Activity 4 - building pions Activity 5 - claims, evidence and reasoning tasks to consolidate the learned rules Activity 6 - comparing the puzzle to real particles systems For more independent students, we propose an open inquiry activity explained in our open inquiry student worksheet. Mission briefing: "Your mission is to use these puzzle pieces to discover the laws that dictate how these particles form groups. You must present your findings as a series of rules that someone else could use to determine possible and impossible combinations of quarks." Limitations of this model: comparing the puzzle to real particles systems Sets of puzzle pieces and additional material There are different sets of puzzle pieces available. The worksheets presented can use either the 3D or 2D puzzle pieces. The activities require only 12 pieces (corresponding to up and down quarks and corresponding antiquarks); however, they can be extended to more quark types. More information about the available sets of puzzle pieces as well as additional information for educators is available at the CERN S'Cool LAB Website https://scoollab.web.cern.ch/quark-puzzle Read more about this activity here: McGinness, L., Dührkoop, S., Jansky, A., Woithe, J. (2019). 3D Printable Quark Puzzle: A Model to Build Your Own Particle Systems. The Physics Teacher 57(8), DOI: https://doi.org/10.1119/1.5131116