# Gene Expression Data Exploration
*Please note, the data present is intended for training purposes only. Information about the data present in this documentation is listed* [*here*](/cohortbrowser/apollo_introduction.md)*.*
When gene expression data is present in your data ingestion for the cohort, the Gene Expression tab will appear in the Cohort Browser. The goal of viewing data within the Gene Expression tab is to view gene expression values in your cohort, and to compare between 2 cohorts within the same data base.
## Features of the Gene Expression Tab
### Overview of the Gene Expression Tab
Within the Gene Expression Tab, there are the following sections: plots for Gene Expression, where you can search for genes by Gene Symbol or Ensembl ID, and an Expression per Feature table. The tables and figures of the Gene Expression Tab are highlighted in the figure below:
### Gene Expression Plots
To view gene expression for a specific gene, type the gene symbol or Ensembl ID into the search bar for the charts labelled “Expression Level”. There are 3 options for the plots: Expression Level with a box plot, Expression Level with a histogram, and a Feature Correlation scatter plot between 2 genes. More than 3 tiles can be added with the “Add Tile” button, and typing in the Gene Symbol or Ensembl ID.
#### Expression Level Box Chart
For the box plot, you can see the distribution of the expression level for a given gene by typing in the gene symbol or Ensembl ID to the search bar. You can view the detailed distribution as a violin plot, or as a box plot. The x axis is the distribution of gene expression levels in the cohort and the y axis is the Expression Level. You can also log 2 or log 10 transform the numeric data. The options to view the detailed distribution are part of the Chart Settings. The Bar Chart with the Violin Plot (detailed distribution) is shown below:
#### Expression Level Histogram
For the histogram, you can see the distribution of the expression level for a given gene by typing in the gene symbol or Ensembl ID to the search bar. You can see the histogram with or without the display statistics. The x axis is the distribution of gene expression levels in the cohort and the y axis is the Expression Level. You can also log 2 or log 10 transform the numeric data. The options to view the detailed distribution are part of the Chart Settings. The histogram with the display statistics settings are shown below:
#### Feature Correlation
For the feature correlation, you can see the expression level for a given gene for the x and y axis by typing in the gene symbol or Ensembl ID to the search bar. You can see the feature correlation with or without the display statistics. The x axis is the gene expression level for one gene and the y axis is the gene expression level for another gene. The options to view the detailed distribution are part of the Chart Settings. The feature correlation with the display statistics settings are shown below:
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