“Progress in science depends on new techniques, new discoveries and new ideas, probably in that order.” — Sydney Brenner

Bread, beer, and the flu are only a few of the many ways microbes welcome us to their worlds. By looking into the microbial realms, modern biology has found the genome-engineering tools to put the right transgenes in the right cells. These tools have changed the way researchers study neural circuits. Nowadays, to study the neurons responsible for specific behaviors, researchers typically screen through a library of pre-engineered animals, each expressing transgenes in a distinct group of neurons, with the hope that one of these neuronal populations controls the behavior of interest. Together with other tools, this library approach accelerated the discoveries of specific neurons controlling feeding, drinking, fighting, and parental behaviors. However, despite great effort, this strategy is still limited by the transgenic lines available and helpless when the relevant neuronal populations do not share a common genetic locus. For example, what if one wishes to study how higher-order, olfactory-processing neurons respond to the smell of apple pie? How can we control these pie-smelling neurons if we don’t know who they are?

In picture: an invisible ghost in front of a green screen. Date unknown.

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