In the top selection box, the virus and the receptor gene are co-selected, i.e. when a virus is selected, the "Receptor" field will turn to the correspondent ones, vice verse.

The Packed bubbleplot display the number of positive cells with selected receptor gene expressed.

Each small bubble represent a cell, concrete expression value will appear when user's mouse move over the cells. Each big bubble represent a cell subtype of selected tissue/organ, and the subtype name is written in the center. As for bigger bubble, the number that appears represent the sum of expression values of the cells within the circle.

User can choose expression threshold to change the "positive level". Only those cells with expression level bigger than the selected number will be shown.