Since their invention in 1963, millions of lamps have been sold across the globe.

And while their popularity has gone through ups and downs, their instantly recognizable style isn't going anywhere.

But what actually goes into creating these iconic lamps?

This simple, yet hypnotic lamp came from pretty humble origins.

Inventor Edward Craven Walker came up with the idea after spotting a handmade egg timer that used heated wax in a cocktail shaker.

And after seeing this and months of testing his ideas and adapting this concept into a colorful lamp, Walker came up with his final design: as it was called at the time, the Astro Lamp.

The idea was patented, and Walker started the company now known as Mathmos.

Mathmos has now been creating lamps for over 50 years, and while it's introduced new designs, the original remains its top seller.

So, how is it actually made?

The process starts with custom glass bottles.

Glass is blown into the shape required for each lamp.

Molten blobs of glass are dropped into a mold.

A machine blows air into the top of the bottle to shape it,

and the newly shaped bottles are then released and cooled.

While this is all done mechanically, everything is checked over by hand.

The bottles are inspected, and any that don't make the cut are discarded.

Quality control is crucial, as each bottle needs to fit perfectly into its housing and the glass need to withstand constant heating and cooling.

The next part of the process is metal spinning, a process that takes a thin sheet of steel and bends it around a spinning tool to create the right shape.

Each base and cap is hand spun, and then the resulting pieces are polished.

Once these two components are finished, the lamp is ready to be filled.

The liquid is added along with a metal spring that helps distribute the heat.

The exact formula of the fluid is a well-guarded secret, but there's one key to it: density.

There are two main components in a lava lamp: a colored wax and a colored solution that it sits in.

As the lamp heats up, the density of the wax changes and it begins to float in the liquid.

When it hits the top, it cools and falls back down.

Getting the density of these two ingredients just right, though, is where the secret knowledge comes in.

Stephen Sharkey: It wasn't a room much bigger than this, but it was split in half.

Teaspoon, chemical, bit of chemistry set, little bit of this, little bit of that.

Does it work?

On the other side was actually a little bit of spinning to make the spinning.

And it sort of evolved from there, really.

Our unique production side is the bottle filling.

There are only a few people here on-site that actually know the ingredients, and there are loads of people in this company that are not allowed to know how that product is made.

Once the two liquids are mixed, the bottle is submerged in hot water.

This water bath cleanly separates out the liquids and stops any wax that would be stuck to the side of the bottle.

Lids are glued on, and the bottles are ready to go.

Mathmos has sold millions of its lamps over the years.

The design is so true to the original that you could still buy the spare parts for a lamp made in 1965.

And at its peak popularity in the '90s, it was selling over 800,000 lamps a year.

Sharkey: I think it represents the '60s, the 1960s, when the world was changing.

The iconic brand, for me, relates to the fact that it's still manufactured here in Britain.

It's still manufactured in the same process.

It's still built in the same place.

But more importantly, it's still part of the original design, which makes it such an icon.