Sesame Street was designed as an experimental research project-a collaboration between television producers, educators, researchers, psychologists, sociologists, child development experts, artists, writers, and musicians. From the beginning, it was a curriculum-driven program emphasizing cognitive, so­cial, emotional, and physical development. Every segment or song was designed to educate young viewers about a specific lesson, and every year the curriculum, created by psychologists and educators, has changed to remain current with the latest findings and suggestions of preschool experts. Young viewers explore letters and numbers as well as subtle but significant messages about love, life, family, and friendship.

     Maintaining an intricate balance between education and entertainment was a constant challenge during the show's development. As material was produced, it was tested on target audiences for appeal and comprehension. The creators initially wanted a show with no fantasy and thus created the urban street setting. When the show was pilot tested in Philadelphia, however, it was poorly received. Researchers discovered that kids lost interest during the street segments and concluded that combining fantasy with reality was necessary.

     Jim Henson's Muppets, built especially for TV, were used to entertain while fulfilling curriculum needs. Initially, the Muppets were not intended to be included in the street scenes but were to appear only in tapped inserts between street segments, animations, and films. Researchers found, however, that children paid attention only when animation and Muppets appeared and concluded that Muppets were integral to the success of the program. Since the first  nationally  aired  episode, Muppets  have interacted  with  the  humans as well as  among themselves in their own segments.

     Big Bird and Oscar were, respectively, the first Muppets  to appear.  Big  Bird, operated since the first episode by Carroll Spinney, represents a six-year-old and, like most of the Muppets, acts as a surrogate child, asking  questions  that  kids  might  ask adults in real life.

     Other original Muppets included Ernie and Bert, Grover, Kermit the Frog, Cookie Monster, and Oscar the Grouch, the trash-can resident whose role is to help kids understand that negative feelings such as anger and irritability are natural. Elmo, representative of a three-and-a-half-year-old, joined the Muppet cast in 1979. In 1999, "Elmo's World" was added as a daily 15-minute segment that closes each hour. It broke new ground in electronic animation while helping children learn to explore their world.

     Some of the early cast of human characters, including Bob (Bob McGrath) Susan (Loretta Long), Maria (Sonia Manzano), and Luis (Emilio Delgado), continue as cast members. Since 1971, Linda Bove has used sign language and provided a positive role model for hearing and non hearing kids. Bove's is the longest­ running role of any physically challenged person in a TV series. Among child performers, the show has always featured children from local elementary schools, mostly from disadvantaged neighborhoods.

     Over the years, Sesame Street increasingly confronted some of life's serious problems. In 1982, the producers used the death of actor Will Lee (fix-it-shop proprietor Mr. Hooper) to address the questions that children inevitably ask when someone dies. In 2001, a series of episodes dealt with rebuilding after a disastrous hurricane. The show also acknowledged marriage, pregnancy, and parenthood with Maria and Luis, who married on the show.

     Sesame Street has become the most widely watched TV series in the world. Taped at Kaufman Astoria Studios in Queens, New York, it appears several times daily on more than 300 Public Broadcasting Service (PBS) stations across the United States. It has been adapted into several international productions , reflecting local languages, customs, and educational needs, and is aired in nearly 150 countries. Seventy percent of American preschool children watch Sesame Street at least once a week. Since the beginning, the show has also attracted an adult audience with its "Who's Who" of singers and actors and parodies of grown-up entertainment (e.g., "Monsterpiece Theater"). The show has hosted more than 250 celebrity guests.

     Sesame Street also sets the record for being the most researched show in television history with more than 1,000 studies on record affirming the show's efficacy and impact. Several establish that educational television makes lasting, measurable contributions to learning. One study concluded that teens who watched Sesame Street when younger had better grades in school, read more books for pleasure, had higher levels of achievement motivation, and expressed less aggressive attitudes than those who watched TV rarely or not at all.

     Sesame Street has won 76 Emmys, more than any show in history. It has also earned Grammys, Peabody Awards, Parent's Choice Awards, the Prix Jeunesse International, a Clio Award, and Action for Children's Television Special Achievement Awards. In its 33rd season in 2002, the show underwent format changes in order to compete with other shows that were aimed at two- to four-year-olds.