A volcano plot places effect size on the horizontal axis and statistical evidence on the vertical axis so researchers can see both dimensions at once.
01
Start with the axes
Points farther left or right have larger negative or positive fold changes. Points higher on the plot have smaller p-values, commonly shown as −log10(p). Neither axis should be interpreted alone.
02
Treat thresholds as decisions
Horizontal and vertical cut-offs are analysis choices, not natural biological boundaries. They should match the study design, multiple-testing method and intended follow-up.
03
Return to the experiment
A striking point can still reflect low counts, confounding, batch effects or an underpowered comparison. Review expression patterns and biological context before prioritising a gene.
