1) The sunflower is not a single flower but a cluster of small flowers arranged in a spiral pattern.

2) The first photograph of a black hole was captured in 2019 using a network of telescopes around the world.

3) The Great Wall of China is a UNESCO World Heritage site and one of the most iconic man-made structures in the world. It stretches over 21,196 kilometers (13,171 miles) and was constructed to protect the Chinese empire from invasions during ancient times.

4) The concept of 3D printing, also known as additive manufacturing, was first introduced in the 1980s and has since revolutionized prototyping and small-scale production.