After watching [Ben Krasnow]’s efforts to build a liquid crystal display ... simple single-segment LCD display out of a pair of microscope slides. It does modulate light, just barely.

In 1888, liquid ... microscope, they noticed that the light passing through the carrot compound (later known as "cholesteryl benzoate") exhibited the refraction effect of a solid crystal when ...

and only in the condition when the liquid crystals were present were the cells protected against the antibiotic. The next step was to see what was happening in single cells under the microscope.