In the post-World War II era, San Diego made a big investment in companies working in atomic energy, medical research and aerospace – realms where San Diego had made a wartime name for itself. That investment helped set the stage for many of the region’s subsequent discoveries. And it helped grow clusters of companies.

Now, half a century later, the landscape has evolved. What are the places, niches, realms where San Diego’s making a mark nationally and internationally? Part of our reporting quest to discover and outline potential barriers to innovation in San Diego is defining what innovation is and where San Diego fits in the larger conversation.

Here’s a tentative list we’ve put together, with the help of some great suggestions, of the areas where San Diego is making a big impact. What did we miss? Let us know below.

Drones, or unmanned aerial vehicles. San Diego boasts two companies at the forefront of drone development: General Atomics (Predator and Reaper drones) and Northrop Grumman (Global Hawk surveillance drones), along with a bevy of support and parts companies. The sector is contributing as much as $2 billion to the local economy, according to a recent report the National University System Institute for Policy Research completed for the San Diego North Chamber of Commerce. A Newsweek/Daily Beast story earlier this year dubbed San Diego “Hub of the U.S. Drone Industry.”

Stem Cells and regenerative medicine. These are the technologies that give humans “the ability to make it the day before yesterday. The day before you find out you have diabetes. The ability to regrow tissues,” said Duane Roth, CEO of Connect, a major organization founded here to foster innovation. Five of the region’s top research institutes teamed up under one roof at what they’re calling a “collaboratory” – the Sanford Consortium for Regenerative Medicine. Several of the companies they’ve spawned with that research are here, too. Search for “San Diego” on this list of prominent stem cell companies.

Genomics. J. Craig Venter, one of the first to sequence the human genome, lives in La Jolla and operates his genetic research institute here. Local companies like Illumina fuse the research with technologies to translate the genetic information into something that can be used to individualize and personalize medicine. “The scientific leadership, research funding/focus and depth of workforce talent and expertise is heavily concentrated in San Diego,” said Mark Cafferty, chief of the San Diego Economic Development Corporation.

Wireless communications. The company Irwin Jacobs co-founded, Qualcomm, pioneered a digital wireless technology the military used to communicate in 1985, and has been patenting new ways to communicate wirelessly ever since. The devices using technologies created here are part of what Qualcomm calls a “digital sixth sense.”

A natural offshoot of this realm, especially amid San Diego’s bustling biotech companies, is to apply wireless technology to health. “Your automobile has 150 or more sensors so you don’t wait until you have smoke coming out of your pipe to know you have something wrong,” Roth said. “We’ll be wearing sensors that keep track of our health.”

Software and software analytics. Software is a huge, amorphous sector that is responsible for a huge number of local jobs. The companies range from the small, early stage startups we featured last week, to large analytics companies. San Diego has had some great successes in analytics companies being acquired (including Urchin, which was bought by Google in 2005). But a big industry group, Software San Diego, is at a crossroads, as its longtime leader stepped down earlier this year, Xconomy’s Bruce Bigelow reported.

There are a few others I heard mentioned in putting together this list that are poised to ascend into these top ranks. (You may think they already belong there – tell us why below.):

• Clean tech: This is the realm for algae and other biofuels, solar power and energy efficiency. Blue tech comprises researchers and companies working on sustainability for oceans – including security, food and transportation perspectives.

• Robotics: Many of the tech/engineering giants listed above are working on technologies that could be part of driverless cars and other vehicles.

• Cybersecurity: Especially as hacking becomes more prominent, an emerging businesses niche aims to protect software and data across tech platforms. The region launched a cluster of such businesses last year.

Mary Walshok, a sociologist who’s been studying the history and next phases for San Diego’s innovation economy, said she hopes the community will embrace a holistic picture of innovation, beyond industries or sectors. Though, she does coin an easy way to think of “the building blocks of our inventive tech economy” – “Phones, Drones and Genomes.”

Beyond those: “Farmers markets, community gardens and craft brewing represent innovative low tech and East Village design district will be the heart of our creative economy,” Walshok wrote in an email.

To that end, a few people highlighted the innovations San Diegans are making in the world of craft brewing. Another recent National University report outlined the economics and proliferation of craft brewers.

These aren’t fringe industries. They represent significant chunks of our local economy.

Total tech jobs in San Diego number 142,000. As a comparison, another big segment in San Diego’s economy, tourism jobs, numbers roughly 160,000.

Here’s how the tech sector breaks down, according to numbers from the state and analysis that National University System Institute for Policy Research economist Kelly Cunningham shared with me.

Software has become San Diego’s single largest tech sector, as measured by number of jobs. Communications (including telecommunications, dominated by Qualcomm) “slipped the past few years,” Cunningham said. Combined, biotech/pharmaceutical industries and other biomedical companies represent more jobs than software, by a slight margin.

Here’s how they’ve changed over the last few years.

Thanks to Cunningham, Walshok, Roth, Lauree Sahba and Mark Cafferty, executives at the San Diego Economic Development Corporation, Jed Sundwall, VOSD super-member and co-founder of a social media startup.

What companies, thinkers, innovators do you think need to be on this list? Please chime in below and help us make this comprehensive.

This is part of our Quest to find out more about the innovation economy in San Diego. Here’s a good overview of what we wanted to find out, and check out these highlights from the series.