In this phase, which typically takes at least three years, we assess how the solution actually works in the real world.
The solution is put into practice on a small scale in one or more locations in the same country or in different countries.
For the whole duration, the experiment is monitored and adjusted if necessary, in order to assess all the facets of the hypothesis that is being tested. The results are collected and discussed, and the solution is evaluated on all the criteria defined in the previous phase.
The outcome of this phase is either a solution that has proved to be good enough to be scaled up or, if the experiment has yielded a negative result, a set of lessons learned that will help to find another, better approach to the problem.