row label on heatmap2

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heatmap label
heatmap label936×812 88.4 KB
heatmap2
heatmap21495×861 50.8 KB

I use heatmap2 to plot some gene expression values, however, the row label of each gene is unreadable; even zoom in, it still massed up. I can’t find the size control option. Anyone can give a help?