Detective Conan is one of the most excelsior (pardon the StanLee phrase if you don't like it, I love this word and he's one of the most talented writers on Earth, one of my all time favorite writers as well) animes to ever get released, like every anime it starts as a successful Manga series.
If you don't know Detective Conan you should get yourself some mangas or get some of the episodes, it is always the best to start with square one (not the children programme with this phrase, I mean start from the beginning) to get the major plot on the character.
He is a brilliant high school student named "Senji Kodo" with noticeble talent in football (the real football, the one called by Americans Soccer). Loving challenges and "Sherlock Holmes" he used his brilliance of deduction to solve crime mysteries police can't solve (the detectives should be ashamed of themselves, more than those of Batman because here a high school kid solves mysteries they can't).
One day returning from a carnival he went to with his girlfriend "Ran Murry" (the girl in the picture) he saw two suspicious guys in black (why can't they let the villain dress colorful for once, always black) doing a deal, one of the guys hit the young eavesdropper on the head and fed him a new type of poison developed in their labs, this poison instead of killing Senji turned him young (reversed puberty, a youth medicine? Silvermaine should've learned that instead of using the tablet of time).
Walking home he discovers he's young again, trying to convince prfessor Agasa (neighbor of the Kodo's) he's the real Senji he uses his power of deduction to tell Agasa where he went, like "Sherlock Holmes" Senji said "Elementry My Dear Dr. Agasa".
In Agasa's lab dressed in a set of clothes he used to wear in his youth he hid from Ran and wore spare glasses of Agasa, when Ran asked him about his name Senji looked back at the book shelf he had his back leaned on and saw a book authored by "Sir Arthur Conan Doyle" (this author got really famous from the fact that people ignored him and believed Sherlock Holmes; his creation to exist in reality) and named himself "Conan Edugawa".
Ran took the little rascal with her home and sent him to an elementry school with three kids he saw in the carnival of the day that changed his life. Conan now is looking for a way to get his puberty back, don't know when the series ended and in what issue. Miss this series and you miss a lot of great entertainment