Bacteria Love Lasered Jell-O

Why don’t we have an arsenal of fast-acting cures for tuberculosis, malaria, and pneumonia? In part it’s because scientists can’t fully understand what they can’t observe: Namely, the way the pathogens that cause diseases and infections live within the human body. The real homes of pathogens—in the blood and tissues of a host organism—are impossible to replicate, so researchers learn what they can by studying these microscopic organisms in petri dishes and test tubes.

These artificial homes for bacteria have been around since the late 19th century, when biologist Robert Koch grew colonies of the bacteria that causes tuberculosis, , in glass test tubes. These vials, and later, glass plates, filled with a gelatinous mix of agar and nutrients, soon filled microbiology labs. “It allowed scientists to identify what bacteria were causing awful, awful diseases like tuberculosis because you could isolate colonies,” says, a Latin phrase that translates as “in glass.”