Just one month ago, there were only two available COVID-19 tests in the country.

Now, that number stands at 32. The FDA's website lists all of the various COVID-19 diagnostics which have been granted emergency authorization—the pace of authorizations has ramped up rapidly.

A perfect storm of failures brought the U.S. to this point. The first coronavirus test, a complex diagnostic developed by the Centers for Disease Control (CDC), simply didn't work, leading to the possibility of inaccurate results. The U.S. chose to develop its own diagnostic rather than use the tests other countries were already using, although the reasoning behind why is unclear.

The Department of Health and Human Services (HHS), cognizant of the CDC test's problems, realized that other tests would have to hit the scene as the agency fixed its own diagnostic. That responsibility would fall to organizations like private firms which could develop commercial tests using their own technologies.

Then came the cascade of FDA emergency use authorizations for such private firms and state health departments. These aren't technically approvals—the approval process for a new diagnostic usually takes somewhere from 12 to 18 months. But given the scope of the coronavirus crisis, multiple firms have been given permission to deploy their own tests.

The CDC's flawed test was authorized on February 4. Next, a test from the New York State Department of Health on February 29.

Two weeks later, emergency authorizations were being granted on a nearly daily basis. First came a milestone authorization for Roche, which developed the first commercially available COVID-19 test in just about six weeks. The company told Fortune it could fuel 400,000 tests per week.

Other prominent companies with tests include: Thermo Fisher Scientific, LabCorp, Quest Diagnostics, Abbott, Cepheid, Cellex, Becton Dickinson, and many others. The latest authorization came on April 8 for a testing kit developed by DiaCarta.

Medical distributor giant Henry Schein also has a test, manufactured by a partnering firm, that didn't require emergency authorization due to the type of test that it is.

There are key scientific—and practical—differences among these various diagnostics. Many of the tests, such as the CDC's and Roche's, are so-called "PCR chain technology" tests. Some are "serology" tests, or blood tests. Some use different variations of these technologies. John Frels, vice president of R&D at Abbott Diagnostics, explained the science to Fortune.

"Commercial companies started coming out with PCR tech-based tests on their platforms," he said, referencing the fact that various federal, state, and local labs need to have the proper equipment to process various kinds of tests. While a test may be able to sniff out the coronavirus, it wouldn't do much good if a laboratory—whether in a hospital, urgent care clinic, or other points of care—doesn't have the right base equipment.

PCR systems are able to churn out hundreds of tests per day—a critical issue to address given America's dearth of coronavirus testing. They're also extremely versatile in being able to detect multiple kinds of infectious diseases, which is why so many major centers already have the equipment.

But there are tradeoffs. Such tests typically require throat and nasal swabs which must be sent off for testing. That can be a time-consuming process taking hours or days.

But with tests such as Abbott's ID NOW COVID-19 diagnostic—a molecular test along the lines of PCR tests, which was given emergency authorization on March 27—you might be able to get a positive result within five minutes and a negative result within 13 minutes at a regional hospital, a physician's office, or an urgent care clinic, which is what the industry dubs as "point-of-care" testing. The equipment required to run the test is also much more portable.

"The next tranche of tests, which are still tests meant to detect the virus' genetic material and active infections, can be done at point of care. But that may be more along the lines of four tests per hour," said Frels of molecular tests.

Why such a big difference in testing time? In order to detect a virus, a test needs to amplify the genetic sequence of the pathogen in a patient's sample. To do that, PCR tests must cycle through multiple temperatures, heating up and then cooling down the sample. ID NOW uses something called "isothermal" technology, which can conduct this amplification process at a more consistent temperature and thus deliver results much faster.

Frels said that Abbott developed its test in a four-to-six week timeframe: "I've never seen anything like this." The company said it plans to ramp up manufacturing to facilitate the delivery of 50,000 tests per day.

And then there's the slew of "serology" tests—blood tests which detect antibodies that were created in response to a coronavirus infection. A serological test has a different use case since it can reveal whether or not someone has contracted COVID-19 in the past and recovered from it, even if they were largely asymptomatic. The CDC reportedly begun deploying such tests as of April 4. Henry Schein's point of care diagnostic is also a serology test, as is a test developed by the biotechnology firm Cellex.

These various tests serve distinct, but important, purposes. And they'll likely have to be used in a multi-pronged approach to coronavirus diagnostics.

"A lot is based on what your facility or your lab has," Pedro Piedra, a Baylor College of Medicine professor and virology specialist, said.

But what can we make of all these tests suddenly coming on to the market—and how would you know which one you're getting, and whether or not it's effective? Piedra, who runs a lab conducting COVID-19 tests, compares the situation to the specter of, well, lasagna. The most important element is the end product, not necessarily the ingredients which go into making it.

"The kind of test you’re getting is largely behind the scenes," he said. "Unless you’re a true connaisseur of lasagna, you don’t really know what the ingredients are."

It can take some time to discern which tests are most effective—not just for coronavirus, but for any disease. But Piedra said that information spreads quickly amongst the medical community and informs health care providers about which tests they should be stocking up on.

"Anything given an emergency authorization needs some data," he said. "Over time, it will be known which ones perform better and which ones perform worse. That situation happened routinely long before this coronavirus came around—your health care provider will be very astute."

But just because testing capacity is ramping up doesn't mean that just anyone can get a test. With the growing number of reported U.S. cases putting a strain on hospitals—as well as divergent public health policies among states based on their number of current infections—one may have to be seriously ill with COVID-19 in order to be given a coronavirus test.

Although the CDC has issued guidance for who should qualify for testing, the agency has also stated that "decisions about testing are at the discretion of state and local health departments and/or individual clinicians."

In some of the hardest hit states such as California and New York, some hospitals are limiting testing to health care workers, those with advanced cases of the disease, and highest-risk populations such as the elderly.

The Trump administration had planned to end federal support for 41 COVID-19 testing sites around the country, but after complaints, the Department of Health and Human Services said it would continue funding. Additionally, the Trump administration issued new guidance this week that would allow licensed pharmacists to order and administer COVID-19 tests, noting that a local pharmacy would be easier to access than having to drive to a hospital or testing site.

Testing access may change as the availability of antibody blood tests ramps up, which is important for a number of reasons. Should the wave of serious COVID-19 cases continue, it would be important to identify those who have recovered and developed an immunity so that they might be able to go back into work and rev up the U.S. economy since they may have a lower chance of re-infection.

While there are still plenty of unknowns about what recovery looks like, Peter Hotez, dean for the National School of Tropical Medicine at Houston's Baylor College of Medicine, believes immunity is likely the case. "From the previous SARS epidemic [caused by a different strain of coronavirus] it was pretty clear people would have antibodies for up to two years and possibly even longer than that. So I’m not as worried about people who have been infected and have developed an antibody response."

The other confusing element behind COVID-19 testing is how much it costs. Multiple firms Fortune spoke with declined to comment on their pricing and distribution strategies.

Theoretically, many of these tests should be free for patients, but there are open questions about how much a patient may be forced to pay out of pocket for a test. Several companies pointed out that it would depend on a patient's insurance status, the specific lab conducting their test, and a host of other complex factors driven by America's fragmented health system.

A number of major health insurance firms including Cigna and Humana have agreed to waive out-of-pocket costs for COVID-19 treatment; Aetna, owned by CVS Health, has made a similar, though more limited, commitment.

But the situation is more unclear for those with other kinds of insurance or no insurance at all. Former Vice President Joe Biden, the overwhelming favorite to win the Democratic nomination for president, has called for Congress to pass a bill that would shield any coronavirus patient from having to pay out of pocket for testing or medical care. The Trump administration has released a plan to help hospitals pay for the cost of treating uninsured coronavirus patients—but, as with everything COVID-19, there are caveats abound.

And then there's the question of when someone is sick and seeks care but turns out not to have coronavirus, or who bears the burden of the costs of a hospital stay before they receive testing.

"Patients could still get big bills from doctors. People who seek care and end up not having COVID-19 could still end up owing full charges," wrote Larry Levitt, executive vice president at the nonpartisan Kaiser Family Foundation (KFF), in a tweet last week.