Comic-Con International at the San Diego Convention Center kicks off this week to a sold-out crowd of more than 125,000 fans and entertainment professionals who share a love for comic books, movies and science fiction.

While comic books were once limited to the static realm of paper and ink, they are experiencing a renaissance in new digital formats.

Major publishers, who were once afraid of piracy, have embraced digital. What's more, online retail giant Amazon just launched its own digital comic book imprint, Jet City Comics, which started publishing and selling original comics earlier this month.

Several startups are poised to tap into this digital shift. A new wave of tech entrepreneurs is trying to give the beloved comic book a facelift by making them easier to access and more interactive.

Here are three startups to watch:

comiXology
Founded in 2007 by David Steinberger, John Roberts and Peter Jaffe after winning a business plan competition at New York University, comiXology sells digital comic books as individual issues and series subscriptions through its online store and app. Its free Comics app was one of the top 10 highest grossing iPad apps last year. The company’s advantage? It managed to get major publishers like Marvel, DC and Image in its digital store early.

Madefire
Launched in 2012 by Ben Wolstenholme, Eugene Walden and Liam Sharp, Madefire is bringing print comics to life by creating digital comic books with motion, sound and interaction. Customers can buy these Motion Books through Madefire’s free app or online reader. In addition to creating original digital stories, Madefire plans to turn major series like IDW’s Star Trek, Transformers, and My Little Pony into Motion Books as well.

Emanata
The comic book industry is often criticized for its dependence on classic series to make money, and for not supporting new, original series. Emanata, founded in 2012 by the founders of Google-owned AdMob, is trying to answer that call and fill the gap by focusing on emerging independent comic books. The free mobile app allows artists to sell their comics and still retain the rights to their work.  

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