Kanye West has surprised his wife Kim Kardashian with a hologram of her late father for her 40th birthday.

The reality star posted a recording of the hologram of Robert Kardashian, who died in 2003.

"For my birthday, Kanye got me the most thoughtful gift of a lifetime," she wrote in the caption.

The video shows Robert Kardashian apparently telling his daughter he watches over her every day, as well as making jokes and dancing.

He is also seen telling Kim she married "the most, most, most, most, most genius man in the whole world".

She described the hologram as "so lifelike" and "a special surprise from heaven".

Lawyer Robert Kardashian was known for defending OJ Simpson at his infamous murder trial in the 1990s. He was played by Friends star David Schwimmer in the 2016 TV dramatisation The People v OJ Simpson.

He can be seen saying: "Happy birthday Kimberly. Look at you, you're 40 and all grown up.

"You look beautiful just like when you were a little girl. I watch over you and your sisters and brothers and the kids every day."

From beyond the grave, he goes on to tell his daughter: "The most beautiful thing that I have witnessed is watching you grow your family...

"You are the most, most, most, most amazing mother to your four beautiful children, and they are perfect.

"Keep doing what you're doing, Kimberley. You are a beautiful soul. Know that I am very proud of you and I'm always with you. I have built a firewall around our family."

Kim and Kanye married in May 2014 and have four children together.

In her accompanying caption, Kim, who was 22 when her father died, wrote: "It is so lifelike and we watched it over and over, filled with lots so tears and emotion.

"I can't even describe what this meant to me and my sisters, my brother, my mom and closest friends to experience together. Thank you so much Kanye for this memory that will last a lifetime.

"Earlier this week, the reality TV star was mocked on social media for revealing she had taken her family to a private island for her birthday.

Keeping Up With The Kardashians, the show which propelled her to worldwide fame, is due to end next year after 20 series.

How does the hologram work?  

It is not clear what kind of technology was used. Kanye may have used a Victorian-era trick called Pepper's Ghost, where a semi-transparent mirror on a stage is used to reflect a film beamed from a projector.

That means it is actually a 2D image displayed on a screen, which itself is invisible to the audience.

Using such technology creates a relatively simple optical illusion - and is used in theatres, museums and theme park attractions such as Disney World's Haunted Mansion.

The Pepper's Ghost technique was used to create Tupac Shakur's performance at the Coachella festival in 2012, at an estimated cost of between $100,000 and $400,000 (£77,000-£308,000).

Alternatively, Kanye may have commissioned an actual hologram - which would have been considerably more expensive. It's also unclear how Robert Kardashian has been voiced.

Technology is increasingly being used to resurrect the dead on stage and screen, but not everyone supports the idea.

A hologram of Whitney Houston toured the UK earlier this year, but the experience received poor reviews.

Plans to feature a CGI version of long-dead actor James Dean in a new film were met with scorn by Hollywood stars such as Chris Evans when they were announced last year.