U.S. billionaire Elon Musk became Twitter Inc's new owner on Thursday after he completed his $44 billion deal to acquire the social media firm, concluding a dramatic six-month saga.

Musk fired Twitter's top executives and gave little clarity over how he will achieve the lofty ambitions he has outlined for the influential social media platform.

Twitter initially resisted Musk's $54.20 offer by adopting a poison pill and later sued the world's richest man after he announced plans to abandon the offer on concerns about spam accounts on the platform.

The tech entrepreneur, whose net worth is nearly $222 billion according to Forbes, has founded, co-founded or is leading the following companies:

COMPANY NAME YEAR FOUNDED WHAT DOES IT DO?

Neuralink 2016 The brain chip startup aims to connect humans and computers.

In July last year, it said it had raised over $200 million from investors including Google Ventures.

SpaceX 2002 The company designs and manufactures aerospace technology, and aims to land its rockets on Mars before 2030. It was valued at over $100 million, CNBC reported last year.

The Boring 2017 The underground tunneling Company company aims to build hyperloops, an ultra-high-speed ground transportation system for passenger and cargo, to solve big city traffic problems.

The non-profit OpenAI 2015 research company was started for the purpose of creating artificial intelligence that augments human capabilities and received up to $1 billion in funding from backers including Musk, LinkedIn co-founder Reid Hoffman and Peter Thiel.

However, Musk decided to exit OpenAI's board in 2018.

Tesla Inc 2003 The electric-car maker, which went public in 2010, is valued at more than $1 trillion, more than legacy automakers Ford and General Motors combined. Last year, Musk said the company will probably launch a "Tesla Bot" humanoid robot prototype in 2022, designed for dangerous, repetitive, or boring work that people don't like to do.

PayPal 1998 The fintech company went public Holdings Inc first in 2002, and was bought by eBay Inc for $1.5 billion soon after. It then went public again in 2015.

The tech entrepreneur's investments in other smaller startups:

COMPANY NAME YEAR FOUNDED NOTES

Stripe Inc 2010 The digital payments company was valued at $95 billion in a fundraising round last year.

Reuters reported in July 2021 that Stripe hired a law firm in its first major step towards a stock market debut.

Vicarious 2010 The artificial intelligence and robotics company, which has received over $250 million in funding, also counts Jeff Bezos and Mark Zuckerberg as its investors, according to its website.

  - Reuters