Econophysics : an introduction Introduction The random walk Beyond the simple random walk Understanding interactions through cross correlations Why care about a power law The log normal and extreme value distributions When a single distribution is not enough Explaining complex distributions with simple models But individuals are not gas molecules And individuals dont interact randomly : complex networks Outlook and concluding thoughts Appendix A : thermodynamics and free particle statistics Appendix B : interacting systems : mean field models fluctuations and scaling theories Appendix C : renormalization group technique Appendix D : spin glasses and optimization problems : annealing Appendix E: nonequilibrium phenomena