RNA-Sequencing (RNA-Seq) is a popular method for determining the presence and quantity of RNA in biological samples. In this 3 hour workshop, we use R to explore publicly-available RNA-Seq data from the Gene Expression Tissue Project (GTEx). Attendees are introduced to the R syntax, variables, functions, packages, and data structures common to RNA-Seq projects. We use RStudio to import, tidy, transform, and visualize RNA-Seq count data. Attendees learn tips and tricks for making the processes of data wrangling and data harmonization more manageable. This workshop does not cover cloud-based workflows for processing RNA-Seq reads or statistics and modeling because these topics are covered in our RNA-Seq Concepts and RNA-Seq in the Cloud workshops. Rather, this workshop focuses on general R concepts applied to RNA-Seq data. Familiarity with R is not required but would be useful.