Xaviera Plooij is a mother of three and the best-selling author and CEO of The Wonder Weeks brand. She lives with her children in the Netherlands. Frans X. Plooij, PhD, has been conducting research in the field of psychology for close to 50 years. Highlights include working alongside his wife, Dr. van de Rijt, with Dr. Jane Goodall on infant development in free-living chimpanzees in the Gombe National Park; leading the department of Research and Development at the institute for Child Studies of the City of Amsterdam; and currently presiding over the International Research Institute on Infant Studies (IRIS) at Arnhem, the Netherlands. He is a full member of several international scientific societies in the domains of child development and behavioral biology and of the New York Academy of Sciences. The late Hetty van de Rijt received her PhD at Cambridge University as a physical anthropologist. With her husband, Dr. Plooij, she studied infant development in free-living chimpanzees with Dr. Jane Goodall in the Gombe National Park. As a researcher at the University of Amsterdam, she studied the development of human babies in their home environment through direct observations, filming, and in-depth interviews with their parents.