Elon Musk's Neuralink has thousands of people lined up for a brain chip implant. Here's what we know about the surgery that replaces a portion of your skull.

The brain chip is about the size of a quarter.

The chip records and transmits brain activity.

The device has ultra 64 ultrathin threads that extend out from the chip.

In total, the threads have more than a thousand electrodes in them.

The threads are designed to go into the brain.

The wires are so small that their width is about 1/14th the diameter of a single strand of hair, according to the company.

The threads are too small to be implanted by a human hand.

That's where a robot comes in.

The device can only be inserted into the brain by a robot, according to Elon Musk.

The robot is able to handle the ultrathin wires, as well as implant them in a way that they avoid disrupting blood vessels in the brain, according to the company.

The robot stands eight feet tall.

Before the robot can insert the device, a human surgeon must remove a portion of the individual's skull.

Bloomberg reported that the craniectomy takes a "couple of hours."

It reportedly takes about 25 minutes for the robot to insert the device.

The device replaces the portion of skull that the surgeon had removed.

Musk has said he wants the surgery to take less time and wants the company to eventually be able to perform the entire surgery without human intervention, Bloomberg reported.

In a human, the Neuralink device is designed to sit behind the ear.

While the device sits behind the ear, electrodes are threaded into the brain

The battery for the brain chip currently lasts "a few hours," but Musk is aiming for it to last about 12 hours, according to Bloomberg.

The device can be recharged using a "custom baseball cap," the publication said.

Neuralink has reportedly done more than 150 implantation surgeries.

The company used the robot to implant the chips into a variety of test animal subjects.

The company has used a variety of the animal test subjects, including sheep, pigs, and monkeys.

In 2021, Neuralink showed how its technology allowed a monkey to play a video game using only its mind.

In a demo video, the monkey, Pager, played a game using a joystick that was disconnected from the game's console — meaning he was controlling the cursor using his brain signals as his arm moved, Neuralink said.

Neuralink rewarded the monkey by feeding it a smoothie through a straw attached to the computer monitor.

Neuralink has received some pushback from animal-rights activists.

The Physicians Committee for Responsible Medicine submitted a complaint about Neuralink to the US Department of Agriculture in 2022 after obtaining more than 700 pages of documents relating to monkeys used in company research at the University of California at Davis between 2017 and 2020.

The group said the records indicated the animals had experienced "extreme suffering."

Both UC Davis and Neuralink denied the claims that the animals were mistreated. And the collaboration between UC Davis and the company ended in 2020.

"At Neuralink, we are absolutely committed to working with animals in the most humane and ethical way possible," Neuralink said in a blog post.