Comment by Kotlopou

Actually, the search here is chemical -- you make a bunch of random small RNA sequences, then chemically replicate those that do what you want, and after a few cycles of this you find just a few sequences dominating the population. The pools can easily reach 10^14 examples and more, because you don't need a separate container/experiment for each one, but do it all together in one batch. The keyword is SELEX, a pretty cool idea: https://en.wikipedia.org/wiki/Systematic_evolution_of_ligand...