The [R][1] package [lavaan][2] ([Rosseel, 2012][3]) is open-source software that makes Structural Equation Modeling (SEM) freely available to a global community of researchers. Its growing popularity as a software option for SEM is due to its [user-friendly syntax][4], widespread community support for applied researchers (especially via a question-and-answer forum hosted by [Google Groups][5]), and the ability of methodological researchers to exploit its flexibility to implement their own newly proposed method in an existing software environment. Almost immediately following its 2010 release, an ecosystem of R packages grew to depend on lavaan, simultaneously enhancing the user experience by providing features for lavaan users that are available in commercial SEM software (e.g., Amos and M*plus*). A [2014 symposium][6] at the [M3 conference][7] first highlighted six such packages: semTools, fSRM, semPlot, lavaan.survey, Onyx, and simsem. In the subsequent 5 years, the success of lavaan and its ecosystem has been marked by the continued development of these packages, as well as a growing presence on the web (not only the [Google Group][8], but [WebSEM][9]) and cutting-edge methods provided by additional R packages. The 2019 symposium at [IMPS][10] (organizer and chair: [Terrence D. Jorgensen][11]) summarized the current state of the early ecosystem and allowed newer contributors to showcase how their latest software developments (individual presentations listed below) extend lavaan in useful and exciting ways. **Featured Packages:** 1. [Gabriella Jiang][29] (equaltestMI package) - on [CRAN][30], on [GitHub][31] 2. [Irini Moustaki][17] (+ [Myrsini Katsikatsou][18]) about [lavaan][19]'s pairwise likelihood estimator for binary/ordinal outcomes - link to [tutorial][20] - supporting papers in *[Computational Statistics & Data Analysis][21]* and *[Psychometrika][22]* 3. Zachary Fisher ([MIIVsem][23] package) - on [CRAN][24], on [GitHub][25] 4. [Ed Merkle][12] ([blavaan][13] package) - on [CRAN][14], on [GitHub][15] - *Journal of Statistical Software* [article][16] 5. Stephanie Lane ([gimme][26] package) - on [CRAN][27], on [GitHub][28] Slides and example syntax are available in the **Files** tab of this project. Additional examples are available in each package's R documentation. [1]: https://www.r-project.org/ [2]: http://lavaan.ugent.be/ [3]: https://www.jstatsoft.org/article/view/v048i02 [4]: http://lavaan.ugent.be/tutorial/index.html [5]: https://groups.google.com/d/forum/lavaan [6]: http://simsem.org/lavaan-ecosystem-M3-2014 [7]: https://modeling.uconn.edu/ [8]: https://groups.google.com/d/forum/lavaan [9]: https://websem.psychstat.org [10]: https://www.psychometricsociety.org/content/recent-meetings [11]: http://www.uva.nl/profile/t.d.jorgensen [12]: https://faculty.missouri.edu/~merklee/ [13]: https://faculty.missouri.edu/~merklee/blavaan/ [14]: https://CRAN.R-project.org/package=blavaan [15]: https://github.com/ecmerkle/blavaan [16]: https://www.jstatsoft.org/article/view/v085i04 [17]: http://stats.lse.ac.uk/moustaki/ [18]: https://www.linkedin.com/in/myrsini-katsikatsou-ab331949/ [19]: https://CRAN.R-project.org/package=lavaan [20]: https://users.ugent.be/~yrosseel/lavaan/pml/PL_Tutorial.pdf [21]: https://doi.org/10.1016/j.csda.2012.04.010 [22]: https://doi.org/10.1007/s11336-016-9523-z [23]: http://gateslab.web.unc.edu/programs/miivsem/ [24]: https://CRAN.R-project.org/package=MIIVsem [25]: https://github.com/zackfisher/MIIVsem [26]: http://gimme.web.unc.edu/ [27]: https://CRAN.R-project.org/package=gimme [28]: https://github.com/GatesLab/gimme/ [29]: https://education.illinois.edu/people/ge-gabriella-jiang [30]: https://CRAN.R-project.org/package=equaltestMI [31]: https://github.com/gabriellajg/equaltestMI