As was introduced in Chapter 1, adaptation is a fundamental attribute of resilient systems. Adaptation could occur by identifying changes in the physical and social environment with the potential to affect a community system operation or by reacting after a disruptive event happens. Part of a positive reaction in the latter of these adaptation mechanisms involves learning about which factors contributed to improving resilience and which factors caused a lower resilience. This chapter focuses on an important tool that is part of such a learning process for improved resilience: disaster forensics. Disaster forensics are based on a postdisaster investigation, in which field investigations and postevent data collection are important components. Hence, the first part of this chapter will focus on explaining the steps and procedures involved with a disaster forensic investigation, including a description of how to perform field investigations. This chapter then describes power grids’ and information and communication networks’ performance in recent natural disasters based on lessons obtained during past forensic investigations.