One of the most common pathways to systems change is to ‘scale’ a successful small-scale innovation.
The theory is simple. Social innovators develop and test a new model or practice that they think can make a positive difference (e.g., improve grade 3 reading rates, protect wetlands, reduce the racism some people encounter when trying to secure good housing). This is usually (but not always) organized as a pilot project. If the experiment is successful, they then work with funders and early adopters to expand the practice broadly enough that it can ‘change’ a system and generate widespread impact.