RainBio is a visual tool for comparing gene sets or protein sets, in a proportional way. RainBio is an alternative to the classical Venn diagrams and Euler diagrams. In particular, RainBio can compare up to 15 sets, while Venn diagrams are limited to 6, and proportional Venn diagram are approximated above 4 sets. RainBio can perform the exact proportional visualization of up to 6 sets, and support intersection clustering, allowing to visualize up to 15 sets. RainBio uses the same file format that InteractiVenn. Several demo datasets are available on the website.