Allan Gregg in Conversation (Video)

History professor William Fowler is the author of "Empire: The Seven Years' War and the Struggle for North America." Fowler maintains that the Seven Years' Was was actually the first global world war. It ended in 1763 with the Treaty of Paris, which marked the emergence of the British Empire, which in turn shaped the world we live in today. (Originally aired January 2006).

Katherine Ashenburg is the author of "The Dirt on Clean: An Unsanitized History" which explores our changing attitudes to washing. From the Romans who made bathing a complete social activity and spent many hours performing their ablutions, to the Middle Ages, when they believed water was the enemy and finally to modern times, when we are almost paranoid about our cleanliness. (Originally aired June 2009)

Katherine Ashenburg is the author of "The Dirt on Clean: An Unsanitized History" which explores our changing attitudes to washing. From the Romans who made bathing a complete social activity and spent many hours performing their ablutions, to the Middle Ages, when they believed water was the enemy and finally to modern times, when we are almost paranoid about our cleanliness. (Originally aired June 2009)

John Fraser is the author of "The Secret of the Crown". He talks about the resurgence of the popularity of the British royal family, which he attributes to the upcoming Diamond Jubilee, the marriage of William and Kate and in Canada, the Harper government's increased recognition of the monarchy as being part of Canada's identity.

John Fraser is the author of "The Secret of the Crown". He talks about the resurgence of the popularity of the British royal family, which he attributes to the upcoming Diamond Jubilee, the marriage of William and Kate and in Canada, the Harper government's increased recognition of the monarchy as being part of Canada's identity.

In his book "The Best of Times: America In The Clinton Years", Pulitzer Prize-winning journalist Haynes Johnson sums up the 1990s as an era of peace, prosperity, scandal, and missed opportunities. It was a time of unprecedented wealth; revolutions were taking place in technology with the world-changing Internet, and in medicine with the mapping of the human genome. However, there was another America dominated by a media filled with scandal and celebrity. 9/11 was definitely a catalyst for change. (Originally aired November 2001)

In his book "The Best of Times: America In The Clinton Years", Pulitzer Prize-winning journalist Haynes Johnson sums up the 1990s as an era of peace, prosperity, scandal, and missed opportunities. It was a time of unprecedented wealth; revolutions were taking place in technology with the world-changing Internet, and in medicine with the mapping of the human genome. However, there was another America dominated by a media filled with scandal and celebrity. 9/11 was definitely a catalyst for change. (Originally aired November 2001)

Pulitzer Prize-winning science writer Natalie Angier, is the author of "Woman: An Intimate Geography", which is an investigation of female physiology and an explanation of how biology affects us as who we are. (Originally aired June 1999)

John Colapinto is the author of "As Nature Made Him: The Boy Who Was Raised as a Girl." The book recounts the tragic story of David Reimer of Manitoba, an identical twin boy who was raised as a girl after a tragic accident to his genitalia. Sadly David Reimer committed suicide in May 2004. (Originally aired March 2000)

Pulitzer Prize-winning science writer Natalie Angier, is the author of "Woman: An Intimate Geography", which is an investigation of female physiology and an explanation of how biology affects us as who we are. (Originally aired June 1999)

John Colapinto is the author of "As Nature Made Him: The Boy Who Was Raised as a Girl." The book recounts the tragic story of David Reimer of Manitoba, an identical twin boy who was raised as a girl after a tragic accident to his genitalia. Sadly David Reimer committed suicide in May 2004. (Originally aired March 2000)

David Shenk is the author of "The Forgetting: Alzheimer's, Portrait of an Epidemic". Shenk talks about this insidious disease, which, because of an ageing population, seems to be reaching epidemic proportions. There is still no known cause or cure although some drugs can mask some symptoms experienced in the early part of the disease. (Originally aired: November 2001)

David Shenk is the author of "The Forgetting: Alzheimer's, Portrait of an Epidemic". Shenk talks about this insidious disease, which, because of an ageing population, seems to be reaching epidemic proportions. There is still no known cause or cure although some drugs can mask some symptoms experienced in the early part of the disease. (Originally aired: November 2001)

Neurosurgeon and CNN medical correspondent Dr. Sanjay Gupta has written a novel, "Monday Mornings". The title refers to the closed-door morbidity and mortality meetings which doctors attend on Monday mornings, to discuss medical errors. Dr. Gupta also talks about being embedded with troops in Iraq in 2003, and performing brain surgery in the field. On the topic of healthcare in the U.S., he believes more should be done to prevent rather than treat diseases. He thinks it is possible to eradicate heart disease.

Neurosurgeon and CNN medical correspondent Dr. Sanjay Gupta has written a novel, "Monday Mornings". The title refers to the closed-door morbidity and mortality meetings which doctors attend on Monday mornings, to discuss medical errors. Dr. Gupta also talks about being embedded with troops in Iraq in 2003, and performing brain surgery in the field. On the topic of healthcare in the U.S., he believes more should be done to prevent rather than treat diseases. He thinks it is possible to eradicate heart disease.