This article by the blog “Being Brunel” illustrates the architectural and structural concepts behind the top 10 tallest buildings in the world (see also wikipedia). Until now the tallest skyscraper ever built is the Burj Khalifa in Abu Dhabi, with its 831m.
However, the Jeddah Tower (previously known as Kindgom Tower) is currently under construction in Jeddah (see wikipedia). When completed, this is going to gain the first place in this chart, reaching 1 km in height. This article by BulldozAri blog describes it.