A spatially fixed library of mutated cells and a method for creating such a library. The library is created by creating a set of cells having a genetic diversity, causing the cells to multiply and express phenotypes, preparing a solution containing the cells diluted in a medium, populating a plurality of through-holes of a testing plate with the solution such that surface tension holds the solution in respective through-holes, and analyzing the phenotypes of the cells in the solution on a hole-by-hole basis. Cells expressing specified phenotypes may then be retrieved.