There were some amazing, headline-inspiring scientific breakthroughs in 2015 -- some sounding like they were torn from the pages of a science fiction novel -- but not all the developments actually matched the hype they generated. Some were more conceptual and preliminary, some exaggerated, and some were spot on. Here's a review of some five the most intriguing.

Printed human organs

Researchers at the University of Florida made headlines in May with a new technique for using 3D printers with organic materials. One of the many challenges in printing organic tissue, like say, a replacement kidney, is maintaining the structure during its construction. Items printed out of metal or plastic have enough structural integrity to hold themselves up while they're only partially completed but organic tissue is too soft to stand alone.

So Professor Thomas Angelini and his team created a way to print organic materials inside of a gel structure. The acrylic acid polymer gel acts as a support, preventing the organic material from collapsing in on itself while it's being printed. That will allow printing things like a detailed model of a patient's organ that a surgeon could practice on before conducting a real surgery.

Still, there are more than a few major hurdles remaining before replaceable organs can come out of a machine. For one, the gel doesn't keep the organic tissue alive. And that means the veins, organs and other body parts produced can't actually be used in a human body just yet.

"Their work is a good first step, but they haven't come even close to printing a functional tissue -- let alone an organ," says Jennifer Lewis, an expert on bio-engineering and a professor at Harvard's School of Engineering and Applied Sciences.

Sunscreen pill

For years, sun worshipers have looked forward to the day when they could skip slathering themselves with messy protective creams and sprays and just take a pill. There are even items on the market today that claim to be sunscreen pills. None taken alone provide the protection of even modest sunblock creams, however.

But a breakthrough from Oregon State University could change that in just a few more years. Scientists have already isolated a natural sunblocking compound called gadusol that is produced by some fish and amphibians (including rainbow trout and alligators).

The OSU team managed to "grow" gadusol in the lab using yeast.

"Certainly intriguing," says Adam Friedman, an associate professor at George Washington School of Medicine and Health Sciences. But there will be "many factors to consider when translating to human intake." Clinical trials on another substance, polypodium leucotomos, found gains when taken in conjunction with sunscreen use for patients with sun sensitive diseases like lupus, he says. Some other products have been tested but "none have come to fruition due to safety concerns."

Truly wireless charging

The dream of an all-wireless future may eventually include recharging our battery-hungry mobile devices as well. Currently, "wireless" recharging refers to placing a smartphone or watch on a charging pad -- no wires required but contact between the unit and the pad must be maintained. Several startups are promising true wireless charging, via energy waves beamed through the air.

Unfortunately, most experts in the field say there's little chance the startups, which rely on converting electricity into sound waves for transmission and then back into electricity, will be able to pull off the promised feat. The problems relate to the basic physics of power transmission. The power of ultrasound broadcasts used to transmit power fade rapidly at modest distances, losing half their strength within 3 meters. And huge amounts of energy are lost converting the signals from power to ultrasound and back to power.

"My gut feeling is that a system of this sort will not be very efficient and will be practical for, at best, limited applications," David Greve, professor in Carnegie Mellon's electrical and computer engineering depratment, told the IEEE Spectrum web site last month.

Nuclear power for all

An Australian scientist and a colleague from Sweden had a radical proposal this year to replace all fossil fuels needed to produce electricity in the world within a few decades -- enough time to actually make a difference and slow down global climate change.

The catch? They wanted to follow the Swedish model of replacing coal and gas with nuclear plants. To keep costs down and speed up the transition, the pair also advocate using old-fashioned fission and water-based reactors, the kind that produce nasty waste that will have to be stored safely for thousands of years.

And that's not likely to get much support around the world, especially in the United States, where nuclear plants are being phased out much faster than new plants are being built. Japan and Germany, too, seem unenthusiastic about current nuclear tech.

But there are some newer designs in the planning stages that could change the entire world's attitude toward nuclear power. Just in the U.S., 43 companies working on more advanced designs for nuclear reactors have raised $1.3 billion. One secretive startup, Tri Alpha Energy, released detailed data this year about gains for its fusion-based technique, called a colliding beam fusion reactor. Fusion reactors should be much safer than the current fission models and produce little waste.

Where's my translator?

The 1960s sci-fi show "Star Trek" imagined a technology that could translate speech from one language to another in real time, in a person's own voice. Fifty years later, the speech-to-speech translator is almost a reality, as Microsoft (MSFT) added speech-to-speech translation to its Skype Translator app.

Speak in Chinese Mandarin, English, French, German, Italian or Spanish and the person you're speaking with hears it in whichever of those langauges they choose. It's not precisely Captain Kirk-level yet. There's a slight delay and the translation is not in the speaker's own voice. But the delays are amazingly small and the speech sounds rather natural, at least for short sentences.