7.1 Types of complexity; 7.2 Intuitive notions of complexity; 7.3 Intrinsic complexity; 7.4 Encoding an object; 7.5 Regularity and randomness; 7.6 Information; 7.7 Algorithmic information content (AIC); 7.8 Effective complexity (EC); 7.9 Physical complexity (PC); 7.10 Bibliography