Kevin Sites in the Hot Zone - Chapter 15: Coming HomeIn this final chapter of "A World of Conflict," Kevin Sites returns home to the U.S., only to confirm what he suspected -- that in the year that he was gone little had changed.

Kevin Sites in the Hot Zone - Chapter 14: Israel-Hezbollah WarThe war between Israel and Hezbollah shook the landscape in the Middle East.

Kevin Sites in the Hot Zone - Chapter 13: Sri LankaKevin Sites covered Sri Lanka as violence erupted between the government and Tamil Tiger rebels, pushing a nation with so much to lose back to the brink of all-out war. In rebel-held territory Sites interviewed Tiger fighters about their tactics and reported on the many effects of war still seen in the region.

Kevin Sites in the Hot Zone - Chapter 12: Nepal and KashmirKevin Sites covered Nepal during a time of sweeping political change that followed mass nationwide protests, forcing the autocratic King to cede power.

Kevin Sites in the Hot Zone - Chapter 11: Child BrideIn Afghanistan, Kevin Sites met a 12-year-old girl named Gulsoma, whose incredible story of resilience resonated with millions of people worldwide. She was only six years old when she was sold to a neighbor family in Kandahar as a child bride.

Kevin Sites in the Hot Zone - Chapter 10: AfghanistanReporting from Afghanistan in spring 2006, more than four years after the U.S.-led coalition ousted the Taliban, Kevin Sites found that war is not over in the country.

Kevin Sites in the Hot Zone - Chapter Nine: ChechnyaIn Chechnya during the winter of 2005-2006, Kevin Sites reported on a region still reeling from lingering conflict between Russia and Islamic separatists. The conflict engulfed Chechnya in the 1990s, and even now, half of the population is yet to return. Those that have eke out a living amid the rubble.

Kevin Sites in the Hot Zone - Chapter Eight: Iran

Kevin Sites in the Hot Zone - Chapter Seven: IsraelIn Israel, Kevin Sites interviewed Kinneret Boosany, a victim of a suicide bombing at a Tel Aviv cafe in 2002.

When Matt Smith stepped into Doctor Who's title role as the 11th Doctor this weekend, he went from British character actor to potential entertainment legend.

The 10 actors who preceded Smith during the sci-fi show's 45-year run are forever linked to the part of The Doctor; some even parlayed the BBC role into a lasting place in pop culture history. Each brought something unique to the role of a benevolent alien traveling through the universe in a stolen time machine, fighting for justice against myriad alien foes.

Smith, 26, will take over from current Doctor, David Tennant, who leaves the show at the end of 2009. Smith, pictured, will first play the Time Lord in the 2010 season.

Hop in the Tardis and take a trip through time with this gallery of Doctors.

1) William Hartnell (1963 to 1966): Hartnell, a veteran character actor known primarily for playing gruff drill sergeants before becoming the first Doctor, went from hostile, mysterious alien to wise and heroic grandfather before stepping away for health reasons.

Distinguishing characteristic: His original anachronistic costume and hair set the tone for his descendants.

2) Patrick Troughton (1966 to 1969): Troughton injected a more playful spirit into the second Doctor, and introduced the spirit of aggressive heroics known in the part today. The talented, quirky actor had a knack for shifting from gleeful mischief to steely resolve in a flash while remaining always compelling.

Distinguishing characteristic: His clownish, "cosmic hobo" outfit was supposedly inspired by Charlie Chaplin.

3) Jon Pertwee (1969 to 1974): An established comedy actor when cast, Pertwee's Doctor might have been the most serious-minded as his exiled and stranded character battled multiple attempts to invade the Earth. The Master (played by Roger Delgado) arrived during this period to torment Pertwee's more active, action-inspired Doctor.

Distinguishing characteristic: Topping off his puffy shirt and smoking jacket, Pertwee's white hair helmet got higher as his tenure progressed.

4) Tom Baker (1974 to 1981): The actor who played the part the longest was also the first Doctor exported to the United States. His performance became sillier as it progressed, but his early and middle seasons pulled down the highest ratings in the show's history, until the show's 21st-century return.

Distinguishing characteristic: Baker has the weird eyes, the beak and a benevolent voice that's kept him working for decades, but it's the 17-foot, multicolored scarf we remember.

5) Peter Davison (1981 to 1984): The youngest actor to play the part until Smith came along, Davison was already a TV star from All Creatures Great and Small when he took the gig. More energetic and manic than Baker, Davison shared the Tardis with a series of younger companions as the show updated its look for the '80s.

Distinguishing characteristic: The fifth Doctor's Edwardian cricket player outfit belied Davison's high energy, and he reportedly hated the costume.

6) Colin Baker (1984 to 1986): A strong actor, Colin Baker was cursed with a poorly re-imagined Doctor-as-arrogant-jerk. As a result, the show struggled and suffered through a hiatus period for the first time in more than two decades.

Distinguishing characteristic: Baker also hated his overdone, mismatched outfit — another symptom of his era's overwrought struggles.

7) Sylvester McCoy (1987 to 1989, 1996): Charming but odd, McCoy packed a lot of authority into his little, gentle-hearted frame. He layered mystery into his performance, but his best efforts couldn't prevent the BBC from canceling Doctor Who after 26 years on the air.

Distinguishing characteristic: McCoy's rich Scottish delivery offered The Doctor's most distinctive voice since Tom Baker's.

8) Paul McGann (1996): Offering a mix of childlike bemusement and heroic urgency, McGann only got to play the part once in an ill-fated American co-production on Fox. But McGann continued on in several audio productions for the BBC and Big Finish Productions.

Distinguishing characteristic: His costume was a mix of Hartnell and Baker, but McGann will always be remembered as the first "leading man" Doctor who got to plant one on the lips of his assistant (Daphne Ashbrook).

9) Christopher Eccleston (2005): An established film and TV star (The Others, Elizabeth), it was Eccleston's job to reintroduce The Doctor to the 21st century. He did so with a tremendous burst of dark, yet heroic and humorous, energy. But Eccleston's stint as The Doctor lasted only one great season before he moved on to other roles in Heroes and G.I. Joe: The Rise of Cobra.

Distinguishing characteristic: Promising that his Doctor would not be a "tosser," Eccleston went with simple black and a leather jacket.

10) David Tennant (2005 to 2009): Tennant, the first actor to play the part who grew up dreaming of being The Doctor, was long rumored for the part before taking over from Eccleston. He became the show's first romantic leading man as he clearly fell for his companion, Rose (Billie Piper), but Tennant's Doctor also seemed like the most wounded, haunted and lonely incarnation.

Distinguishing characteristic: Whether it was the suit or his carefully managed hair, Tennant's look was engineered to draw in the ladies.