Understand anything, one simulation at a time.
Eight interactive explainers across networking, physics, earth science and biology. Press play, step through, or jump straight to the part you're curious about.
How the internet works
Follow a single request from your laptop to a distant server and back — through your router, an ISP, and the servers that answer.
Steps
Key facts
- Data is broken into small chunks called packets before it travels.
- Each packet can take a different route and gets reassembled at the destination.
- DNS translates a readable name like example.com into a numeric IP address.
- A typical request completes a full round trip in well under a second.
How IP addressing works
Every device on a network needs a unique address. See how a subnet mask splits an IP address into a network part and a host part.
Steps
Key facts
- An IPv4 address is 32 bits, usually written as four numbers 0–255.
- A subnet mask marks which bits identify the network versus the individual host.
- Devices on the same network can talk directly; others need a router.
- /24 is the most common home-network prefix — 256 addresses, 254 usable.
How lightning happens
Inside a storm cloud, colliding ice and water build up a massive electrical charge — until it discharges in a fraction of a second.
Steps
Key facts
- Collisions between ice crystals and soft hail separate positive and negative charge.
- Negative charge collects near the cloud base; positive charge gathers on the ground below.
- A stepped leader feels out a path, then a bright return stroke surges upward.
- A bolt can reach roughly 30,000°C — hotter than the surface of the sun.
How rain forms
Water is constantly cycling between the ocean, the sky and the ground. Watch it evaporate, condense into clouds, and fall back down.
Steps
Key facts
- The sun's heat evaporates water from oceans, lakes and rivers into vapor.
- Rising vapor cools and condenses onto tiny particles, forming cloud droplets.
- Droplets collide and merge until they're heavy enough to fall as rain.
- The same water molecule can cycle through this loop for thousands of years.
How atoms work
Every atom is mostly empty space: a dense nucleus of protons and neutrons, orbited by electrons in shells.
Steps
Key facts
- Protons (positive) and neutrons (neutral) sit together in the nucleus.
- Electrons (negative) occupy shells around the nucleus, held by electric attraction.
- The number of protons defines the element — carbon always has six.
- If the nucleus were the size of a marble, the atom would be the size of a stadium.
How earthquakes happen
Tectonic plates grind against each other along a fault line, storing up strain — until it releases all at once.
Steps
Key facts
- Earth's crust is broken into large tectonic plates that slowly move.
- Friction along a fault locks the plates together while stress keeps building.
- When the stress overcomes friction, the plates slip suddenly, releasing energy as seismic waves.
- Aftershocks happen as the surrounding rock adjusts to its new position.
How fertilization happens
A simplified, textbook-style look at the cellular process that begins human reproduction — from release to the first cell division.
Steps
Key facts
- Fertilization is the fusion of a sperm cell and an egg cell into a single cell.
- Of the hundreds of millions of sperm released, typically only one fertilizes the egg.
- The egg's outer layer changes instantly on contact, blocking any other sperm from entering.
- The fertilized cell divides repeatedly over the following days as it travels to the uterus.
How vaccines work
A vaccine trains the immune system to recognize a threat safely, before it ever meets the real thing.
Steps
Key facts
- A vaccine shows the immune system a harmless piece or weakened form of a pathogen.
- Immune cells learn to recognize it and produce antibodies against it.
- Memory cells remain afterward, ready to respond fast if the real pathogen ever appears.
- That faster, stronger second response is what usually prevents illness.