References

Reference We take a closer look to see if using air purifiers helps with asthma.

REFERENCE Air purifiers can improve air quality, but do these devices help relieve allergies?

Learn how to capture the night sky — tips on choosing the best camera and lens, plus advice on camera settings, choosing a good location and apps to help plan your shoot.

Master the basics with this beginners guide to wildlife photography. Find the best cameras, learn how to find your subjects, and handle changes in lighting.

Discover interesting facts about elephants, the highly intelligent and social animals that roam Africa and Asia.

Discover interesting facts about octopuses, an intelligent group of cephalopods with three hearts, eight arms and a reputation for causing mischief in oceans around the world.

Discover interesting facts about how big earthquakes can get, why earthquakes happen, and why they're so hard to predict.

Discover interesting facts about orcas, the deadly and beautiful predators that lurk in every ocean.

Discover interesting facts about where sharks live, how big they can get, and how likely it is to get bitten by one.

The deadliest cancers aren't necessarily the ones that kill the most people overall; they're the ones with the lowest survival rates.