Some infectious diseases like malaria, leishmaniasis, or HIV, establish chronic, latent infections in places of the body that are very difficult to reach and study, such as the bone marrow. These hidden reservoirs allow the pathogen to evade immune responses and drug treatments. They also make it very hard for scientists to observe what happens directly in patients, both for technical and ethical reasons.

To overcome this challenge, researchers are increasingly using organ-on-a-chip technology: tiny devices in which human cells are grown to mimic the structure and behavior of human organs in the lab. These chips often contain gels that imitate the 3D environment of our tissues.