It is not exactly Newton having an apple fall on his head, but in terms of practical application it might be just as useful.
It was 1998 and Clemens Bimek had just come back from a hard day at work at his carpentry workshop.
Propping himself up on the sofa, he put the TV on and started watching a documentary on contraception.
When the show got into a detailed description of how sperm flows through the seminal ducts into the penis, Bimek asked himself “Why wouldn't you just build a valve in there?”
Through chance, the carpenter's route to work took for took him past the patent office and one day he decided to take a look in, to see if his idea had already been patented.
While he found that some patents had already been made in this direction, he found the ideas too complicated.
So he set out to make his own sperm switch.
What he has since developed - branded the Bimek SLV - has been proclaimed by some urologists as revolutionary.
In the one implant which has so far been conducted - on Bimek himself - medical tests have proven that the switch is effective at cutting of the supply of sperm to the penis.
It has a great advantage over vasectomies in that it is flexible, urologist Hartwig Bauer told Der Spiegel.
“A third of all patients would like to have such operations reversed at a later date. But it doesn't always work,” Bauer said.
The "gummy bear-sized" valve is placed into the seminal ducts in a simple operation and can then be switched off or on by its owner depending on his needs.
The operation to have the device - which is 1.8 cm long and weighs 2 grams - implanted would take around half an hour. And, once in, the device remains in working condition for the rest of your life, the company behind the project claims.
The advantages of the device are clear - women would no longer need to bear the burden of taking contraception - and hormone altering pills would become a thing of the past.
But some urologists remain sceptical.
Wolfgang Bühmann, spokesperson for the Society of German Urologists, told Spiegel that the valve could have negative side effects.
“I believe that the implantation of this valve could lead to scar tissue building up in the seminal ducts,” the doctor said, warning that this could stop sperm travelling through the tubes.
The specialist further worries that sperm could stick to the valve which could clog up the switch mechanism over time.
What is certain is that there is still a long way to go before the valve will be available to the general public.
First tests on the product are set to start early this year, with the valve being implanted into 25 men.
“Other implants made of this material have already been used in other regions of the body without complications. The question is whether there will be problems when it is implanted in this area,” Anneke Loos, head of the test centre for medical products in Hanover said.
To gain the necessary certification for his product Bimek is now seeking investment to the tune of €5 million, including through a crowdfunding campaign.
All this could take time, meaning that at the earliest the Bimek SLV will be available to the public in 2018.