1) The word "oxygen" contains two vowels: O and E.

2) Orchids are one of the largest families of flowering plants, with over 25,000 species.

3) The Northern Lights, also known as the Aurora Borealis, are natural light displays that occur in the polar regions due to interactions between the Earth's magnetic field and solar particles.

4) The novel "To Kill a Mockingbird" by Harper Lee has been translated into more than 40 languages and has sold over 40 million copies worldwide.