Our last section deals with infill development.  Infill is a loosely defined term that refers to development projects on vacant urban land or the redevelopment of a blighted building or neighborhood.  Another way to look at this is how the neighborhood evolves over time.  Infill development within existing urban areas conserves environmental resources, economic investment, and social fabric, while reclaiming marginal and abandoned areas.  It is crucial for new buildings to fit in with existing structures; this can be done successfully using the design principles discussed in earlier sections.