Idiom #3 : Reinventing the wheel
To reinvent the wheel is to duplicate a basic method that has already previously been created or optimized by others.
The inspiration for this idiomatic metaphor lies in the fact that the wheel is the archetype of human ingenuity, both by virtue of the added power and flexibility it affords its users, and also in the ancient origins which allow it to underlie much, if not all, of modern technology. As it has already been invented, and is not considered to have any operational flaws, an attempt to reinvent it would be pointless and add no value to the object, and would be a waste of time, diverting the investigator's resources from possibly more worthy goals which his skills could advance more substantially (source: Wikipedia)
Eminem's progressive rap style has raised the bar for Hip-Hop lyricism across the board. [...] he's continued to reinvent the wheel, putting his life on display, through a bevy of syllable-heavy, metaphor-driven cuts (source: Stack Exchange)
Photo insert. http://www.sidseldorphjensen.com/wp-content/uploads/2013/06/reinvent1.gif