It doesn't take a genius to realize that we're in the midst of a housing crisis right now. Numerous major cities are pricing out many of the people that live there with extortionate and ever-increasing rent prices, and that's only if there are enough places to live for everyone who needs them (spoiler alert: there never are).
Realistically speaking, not everybody is going to have the tools to uproot their lives and go elsewhere — or indeed want to, for that matter. It's no secret that most urban areas are going to need more and more affordable housing over the coming years, but with space and planning restrictions, this can sometimes be easier said than done.
Identifying how in some areas building was restricted by height, @AaronBergman18 proposed an unconventional 'solution', complete with detailed diagram from an article about underground bunkers. Suggesting that developers start building apartment blocks below the earth, his idea was swiftly ratio'd by other Twitter users who were keen to point out the multiple flaws in his plan. Practical considerations aside, turning us all into mole people probably wouldn't be the best idea for our vitamin D levels, or our sanity, either.