Insurance products often deal with more than just “alive” or “dead”. They must track health events like becoming too sick to work, being diagnosed with a serious illness, or needing long‑term care. In all these cases, a person moves through distinct health states, and the timing of those moves determines what the insurer pays out. This chapter shows how multi‑state models help us design, price, and reserve for four major lines of business: disability income, critical illness, long‑term care, and even the modelling of HIV/AIDS for health insurance.