Migration has become a heterogeneous phenomenon today, with the emergence of migration lying in the quest of human beings to obtain a better life. However, this is not the sole factor for migration because some migrate for sheer survival while others migrate to improve their quality of life or search for fortune. The dominant explanatory model used in the study of migration has been Ravenstein's fundamental model. This book presents and discusses a number of such models which present information on the history of human mobility.