<p>Section 1. Background<br>1. History of Twin Studies<br>John C. Loehlin<br>2. Prevalence of Twinning Worldwide<br>András Pári<br>3. Twin Family Registries Worldwide<br>Yoon-Mi Hur, Veronika V. Odintsova, Juan R. Ordonana, Karri Silventoinen, and Gonneke Willemsen</p> <p>Section 2. Phenomenon of Twinning<br>4. Biology of Natural Twinning<br>GARY David STEINMAN<br>5. Management and Outcome of Twin Pregnancies<br>Gian Carlo Di Renzo, Valentina Tosto, Irene Giardina, Valentina Tsibizova<br>6. Conjoined Twins<br>Julia Metneki and Peter Varjassy</p> <p>Section 3. Twin Families<br>7. Growing up as Twins: The Perspective of Twin Researchers<br>Adam Domonkos Tarnoki, David Laszlo Tarnoki, Julia Metneki and Nancy L. Segal<br>8. Parenting of Twins, Triplets, or More<br>Monica Rankin<br>9. Reared Apart Twins: Background, Research, Case Studies and What They Reveal About Human Development<br>Nancy L. Segal and Francisca J. Niculae<br>10. Opposite-sex Twins in Medical Research<br>Lucas Calais Ferreira, Sue Malta, and John L. Hopper</p> <p>Section 4. Twin Methodologies<br>11. Establishing a resource for genetic, epidemiological and biomarker studies: the important role of twin registers<br>Veronika Odintsova, Gonneke Willemsen, Conor V. Dolan, Jouke-Jan Hottenga, Nicholas G. Martin, P. Eline Slagboom, Juan R. Ordoñana, Dorret I. Boomsma<br>12. Methodology of Twin Studies<br>José J. Morosoli, Brittany L. Mitchell, and Sarah Medland<br>13. Twin Studies of Complex Traits and Diseases<br>Christopher R. Beam, Alice J. Kim, and Tinca J.C. Polderman<br>14. Use of Twin Studies to Make Inference About Causation for Measured Exposures by Examining Familial Confounding<br>Vivienne F. C. Esser, Shuai Li, Minh Bui, and John L. Hopper<br>15. Twin Research in Clinical Trials<br>Athula Sumathipala and Kaushalya Jayaweera</p> <p>Section 5. Behavior<br>16. Twin Studies in Social Sciences<br>EIena Cristina Mitrea and Levente Littvay<br>17. Childhood Development of Psychiatric Disorders and Related Traits<br>Isabell Brikell, Paul Lichtenstein, and Henrik Larsson<br>18. Happiness and Well-being: The Value and Findings from Genetic Studies<br>Margot P. can de Weijer, Lianne P. de Vries, and Meike Bartels<br>19. Twin Studies of Personality<br>Juko Ando<br>20. Twin Research in Psychopathology<br>Lisabeth Fisher DiLalla, Matthew R. Jamnik, Riley L. Marshall, Emily C. Pali, and David DiLalla<br>21. Cognitive Aging: The Role of Genes and Environments in Patterns of Change<br>Deborah Finkel, Nancy L. Pedersen, and Chandra A. Reynolds<br>22. Twin Studies of Smoking and Tobacco Use<br>Jaakko Kaprio</p> <p>Section 6. Health<br>23. Anthropometric Twin Studies<br>Karri Silventoinen<br>24. Twin studies of cardiorespiratory disease, daily cardiovascular activity and imaging<br>Adam Domonkos Tarnoki, Gonneke Willemsen, Eco de Geus, and David Laszlo Tarnoki<br>25. Pediatric Twin Studies<br>Catarina Almqvist and Paul Lichtenstein<br>26. Twin-Singleton Differences<br>Kaare Christensen and Matt McGue<br>27. Twin Studies of Puberty and Behavior<br>Holly T. Pham, Adriene M. Beltz, Robin Corley, and Sheri A. Berenbaum<br>28. Muscoloskeletal Twin Studies<br>Paulo Ferreira and Munkh-Erdene Bayartai<br>29. Contributions of Twin Studies to Cancer Epidemiology<br>Wendy Cozen, Esther Lam, Maryam Salehi, Victoria K. Cortessis, Tuong L. Nguyen, James Dowty, John L. Hopper, Shuai Li and Thomas M. Mack<br>30. Epigenetic Studies of Neurodevelopment in Twins<br>Jeffrey Mark Craig, Namitha Mohandas, Yuk Jing Loke, Jennifer Eleanor Snowball, Yen Ting Wong and Garth Stephenson<br>31. Contributions of Twin Research to the study of Alzheimer's Disease and Related Dementias<br>Matthew Sebastian Panizzan, Jeremy Elman and Eero Vuoksimaa</p> <p>Section 7. Twin Research: Genetics, Epigenetics, Microbiome, and Environmental Adaptation<br>32. Twins and Omics: The Role of Twin Studies in Multi-Omics<br>Fiona Alysa Hagenbeek, Jenny van Dongen, Rene Pool, and Dorret I. Boomsma<br>33. Epigenetics<br>Aino Heikkinen, Sara Lundgren, and Miina Ollikainen<br>34. An Experiment in Co-Twin Control: Adaptation to Space Travel<br>Carole Tafforin and Nancy Segal<br>35. Environmental Risk Factors for Neurodevelopmental Disorders: Evidence from Twin Studies<br>Garth Stephenson and Jeffrey Mark Craig<br>36. Microbiome Studies and Twin Research<br>Joohon Sung, Hang A. Park, and Sooji Lee<br>37. Chromosomal Anomalies, Monogenetic Diseases, and Leukaemia in Twins<br>Iren Haltrich and Anna Lengyel</p> <p>Section 8. Conclusion<br>Summary<br>Adam Domonkos Tarnoki, David Laszlo Tarnoki, Jennifer Harris and Nancy Segal<br>Appendix: Resources, Websites, Twin Organizations, and Further Reading<br>Adam Domonkos Tarnoki, David Laszlo Tarnoki, Jennifer Harris and Nancy Segal</p>