Tesla CEO Elon Musk has sent out a memo to employees reminding them that working from home is not acceptable. The notice, sent out early Wednesday morning at 2:30 am, states that "office is not optional". The memo comes as Tesla is set to hold its investor day on September 22nd, where the company is expected to discuss its plans for the future. The memo is not the first time that Musk has taken a hard stance on the issue of working from home. In May, he tweeted that "remote work should be the exception, not the rule" and that employees should be "physically present". The memo has been met with mixed reactions from employees. Some feel that it is a necessary reminder of the importance of being in the office, while others feel it is unfair to those who have been working from home for months. It remains to be seen if the memo will have an effect on Tesla's investor day, or if the company will continue to allow employees to work from home. In the meantime, investors will be watching closely to see what Tesla has in store for the future.