His success helped change Marvel Comics from a small publishing house to a large multimedia corporation.

In his teens Lee began working for publisher Martin Goodman as a copyboy at Timely Comics. A text filler page for Captain America comics under the pen name Stan Lee was his first published comics work. He soon graduated from filler to writing actual comics, then became the youngest editor in the field at 17.

During World War II Lee enlisted in the US army, and served in the Signal Corps writing manuals, training films, slogans, and occasionally cartooning. His military classification was "playwright"; only nine men in the US Army were awarded the title.

Returning to his position at what would become Marvel Comics, Lee produced titles in a number of genres.

In 1961 Lee and artist Jack Kirby produced the Fantastic Four. Its immediate popularity soon led to Lee producing a cavalcade of new titles such as The Incredible Hulk, Daredevil, the X-Men, the Mighty Thor, and many others.. On a smaller scale and for a shorter time, Lee also enjoyed a highly successful artistic partnership with artist Steve Ditko which included Doctor Strange and Marvel Comics' most successful character of all, Spider-Man.

Lee scripted and edited most of the comics published by Marvel in the 1960s, moderated the letters pages, and wrote endless promotional copy. To maintain his taxing workload yet still meet deadlines, he developed what is known as the Marvel-style of comic scripting. Aided by capable artists, Lee would first brainstorm or provide a brief synopsis of a story rather than a full script. Based on the synopsis, an artist would then flesh it out into the allotted number of pages. After the artist turned in penciled pages, Lee would add dialogue and captions. In effect the artists were co-writers, whose first drafts Lee built upon.

The exact division of creative credits on Lee's comics is still disputed, especially those drawn by Jack Kirby and Steve Ditko. Some argue Lee hogged the credit for stories and characters while shortchanging the artists. Others doubt this, including Lee himself who has always effusively praised these artists; the illusion may stem from out-of-context quotations by journalists, plus Lee's bad memory and tendency to overpraise all co-workers equally.

Lee helped reinvent the genre of the superhero comic. He gave the superhero a flawed humanity. His heroes had bad tempers, melancholy fits, vanity, greed, etc. They bickered amongst themselves, worried about paying their bills and impressing girlfriends, and were often ill. Lee wrote characters readers related to rather than idealized.

By accident Lee reformed the Comics Code Authority. This came about when he was asked by the US Department of Health to write a comic about the dangers of drugs. Lee agreed and wrote a suitable Spider-Man story, slated to be published in Amazing Spider-Man #96. The CCA refused it because it depicted drug use and the context in the story was considered irrelevant. With publisher Martin Goodman's approval, Marvel published the comic without the CCA seal of approval. The comic sold well and Marvel won praise for having a social conscience. The CCA subsequently loosened the code to permit negative depictions of drugs.

In later years, Lee became a figurehead and public face for Marvel Comics. He made appearances at comic book conventions around the country, lecturing and participating in panel discussions. Lee moved to California in 1981 to develop Marvel's TV and movie properties. He has been an executive producer for, and has made cameo appearances in, recent Marvel film adaptations.

During the dot-com boom, Lee lent his name and likeness to StanLee.Net, an online multimedia company administered by others. Unfortunately the company became infamous for its mismanagement and dubious accounting.