NPR has a nice video on their website with a playful visualization of how humanity grew to count 7 billion living people. Using more or less leaky glasses as a metaphor, the video visualizes the population growth which has been taking place in different regions of the world since AD 1000.
Hitting the 7 billion threshold has seen many maps and visualizations on the internet, but I like this one especially, for it’s simple and clear yet nicely explains the concept of net growth resulting from different trends in human mortality and fertility.