For starters, this show had one of the greatest theme songs in TV history. Even as an adult, if you hear the opening theme, you will be blown away by how good it still is.
The show itself is very hard to track down, but the show succeeded by blending together a 3 basic elements.
First there were the hosts of the show who hung out in a cool activity room chatting with each other and doing various science related activities related to the episode's theme. There were usually mild soap opera concepts thrown into these segments and sometimes there was an ongoing plotline that would continue from one day to the next. The primary purpose of these clubhouse scenes was to introduce short documentary clips of the various hosts out in the world learning a scientific principle.
Lastly, there was the Bloodhound Gang, which was a short 5 minute mystery show featuring a gang of kids who solved small crimes. The mysteries would usually be extended over a few episodes.
The format stayed the same for the entire run of the show, however, there were two versions of the clubhouse. The first and best clubhouse contained 3 high school/college age teenagers, two girls and a guy. The banter and chemistry between them was quite fun as they often mildly teased each other in a semi-flirtatious manner.
After the first season, the clubhouse gang and clubhouse changed completely. Suddenly there were more people in the gang, and they were in a basement in New York. Also there was a kid, who was mainly there for Scrappy-Doo style comic relief. This team remained in place for the remainder of the show's run. While they are perfectly fine, the first season was really the best, and would be the better shows to try and track down.