One by one, companies are staking out different animal tissues to grow in vitro for human consumption. First there was beef. Then there was chicken. Now there's pork.

San Fransisco-based startup Memphis Meats made its public debut today, with a Wall Street Journal exclusive that details the team's ambitious plan to grow beef and pork in laboratory bioreactors—and to be the first company to bring lab-grown meat to market. Memphis Meats says it'll be selling its animal-free products to high-end customers in three to four years. Oh, and to dissuade any lingering doubts, they've also just unveiled the world's first lab-grown meatball.

Mark Post, whose stem cell burger created an international sensation in 2013, recently announced that his company, Mosa Meat, would be selling lab-grown beef in four to five years.

Mark Post, whose stem cell burger created an international sensation in 2013, recently announced that his company, Mosa Meat, would be selling lab-grown beef in four to five years.

Lab-grown meat is one of those futuristic technologies that polarizes people, with some saying it's going to replace animal agriculture and others insisting it'll never be more than a novelty. Most arguments for or against lab-grown meat hinge on whether you buy the claim that we can produce animal tissue in laboratories at a far lower per capita cost than we can growing it the old fashioned way.