What is Chaos Engineering and how do you implement it?

Chaos Engineering proactively tests system resilience by introducing controlled failures. Process: define steady state, hypothesize impact, run experiment, measure, learn. Principles: start small (staging), minimize blast radius, automate experiments, run in production (carefully). Tools: Chaos Monkey (random instance termination), Gremlin (comprehensive platform), Litmus (Kubernetes), ToxiProxy (network failures). Examples: kill instances, inject latency, simulate region failure. Requires mature observability. Document runbooks from learnings. Game days formalize chaos experiments.