Most of us don’t think of the sewers as an exciting place. But these and other waterways are where Rolf Halden is finding and solving many mysteries.

Knowing when you are sick and what illness you have is the first step to helping your body fight back. Immunologist Douglas Lake gets to design and build tests that can tell us what virus we have, or how well our body is fighting it.

Play the Cell Size SIM

Certain cell types should have a general size and have proportionate parts. But what if those sizes and proportions are different than they should be? The size of the nucleus versus the size of the cytoplasm in a cell is an important measure – it can tell us if something might be wrong with that cell. Explore more about this "NC ratio" in Cell Size SIM.

To learn more about cells, visit The Building Blocks of Life.

When a virus infects our cells, it can do a lot of damage. But, in some cases, certain viruses get into a cell and go dormant, kind of like they are taking a nap. If we are going to better fight viruses, we need to know what viruses do when they are dormant.