With three decades of educating and entertaining children under its belt, the Children's Museum of Manhattan is now at that poignant time of its existence when it's older than some of the parents who bring their kids there. The chances are excellent that many of today's parents romped through the museum themselves as youngsters — and there's no reason not to expect, in 20 years' time, to see them coming back with their kids again, with grandchildren in tow. Although not the oldest children's museum in the city, CMOM is certainly one of the busiest, with its doors yanked open by more than 350,000 visitors yearly. Carry that number — at least that number — forward for another three decades, and you'll have scores of New York families with senior members who can talk about their CMOM memories going back to childhood. CMOM has been successful because its exhibitions have been smart, creative, and entertaining — and often cozily familiar in subject matter. It's not necessary to go very far back to find examples: Since 1999, the museum has done shows on the science of the human body, Mister Rogers Neighborhood, Peanuts creator Charles M. Schulz, Maurice Sendak, and Beatrix Potter. Last year, the museum turned its attention to various aspects of fine art, serving as the New York venue for the cleverly interactive Chagall for Children, and even bringing in blue-chip artists Elizabeth Murray, William Wegman and Fred Wilson to create three-dimensional versions of their signature works for Art Inside Out. (Art Inside Out will continue to run through September). Now, in celebration of its 30th year, CMOM is as on-top-of-it as ever, with four major interactive exhibits turning the spotlight on everything from Arnold Lobel's classic Adventures with Frog and Toad books, to forensic science. (You heard right). Having recently made a big splash at the Cort Theater in the form of the musical A Year With Frog and Toad, the characters (a calm frog and an edgy toad) and their world will be center stage at the museum through December during its interactive exhibit that includes storytelling, sing-a-longs, and songs from the show, presented on Thursdays, Saturdays and Sundays by the museum's own performers. For young Sherlocks, Court TV's "Mobile Investigation Unit", or MIU, is making its second national tour, by popular demand, with a new caper called the MIU Kloos Family Mystery. Using interactive kiosks, kids will scour a simulated "caper scene" to gather clues like fingerprints, hair and fiber samples. Their findings will help crack the mystery of who lifted the Kloos family laptop, which contains such secrets as Grandma Kloos' cookie recipe and Mike Kloos' chili contest recipe. Suspects are the Kloos' State Fair competitors, and there's a suspect for each family member, so be on the ball. The sleuthing goes on through September 1. (On a more serious note, the museum will once again continue to keep kids safe by offering a Forensic Profile of each visiting child, including fingerprinting and a photo that parents can take home. The service is provided by the MIU, in conjunction with the KlassKids Foundation. Last year, more than 25,000 kids were fingerprinted). From examining clues to focusing in on the environment, the museum's "My Home Planet Earth" is a bilingual exhibition that looks at smaller, and sometimes invisible inhabitants, in aspects of the environment such as air and water pollutants, mold spores and dust mites. A 2,000-square-foot interactive exhibit, "My Home Planet Earth", puts kids in the fictional town of Bright Water Corners, where the world of squirrel cousins Riff and Rosie, along with their beaver/scientist friend Castor Slaptail, serves as the setting for kids to uncover and solve environmental health issues in the animals' homes. More than a dozen interactive activities are planned around the exhibit; kids ages 5-10 are encouraged to scoop up mucky water samples from the marsh for research, and use recycled materials to build their own inventions at Mr. Slaptail's workbench. (They're also invited to trace the route of dust particles through a giant nose — this writer’s personal favorite). Riff and Rosie will make personal appearances throughout the course of the exhibition, which runs through September 1; to find out when, call (212) 721-1223 or go to www.cmom.org. The museum's "Seeing the Story" series continues this summer with "Travels with Ted and Betsy Lewin". Married since 1963, the couple shares a deep affinity for both animals and illustration; books such as Gorilla Walk are true accounts of their travels. (Gorilla Walk is a record of their visit to the Bwindi Impenetrable National Park in Uganda, illustrated with Ted Lewin's extraordinary watercolors). The present exhibition, which continues until November, puts the couple's talents on full, and deserved, display. "City Splash" gives hot summer kids the chance to cool off while learning all about the not-so-simple element of water. As always, exhibitions and art workshops will keep kids busy in the Russell Berrie Art Studio; while the Early Childhood Center continues to offer a range of creative activities for the museum's youngest visitors. As for colors and shapes — always part-and-parcel of teaching the young — they're the subjects, via digital imaging technology, at the museum's HP Inventor Center. Happy Big 3-0, CMOM. For more information, call (212) 721-1223, or go to www.cmom.org.