Travel
Science Museums in Washington, DC: Where to Go and When
November 1, 2026
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Travel
Science Museums in Washington, DC: Where to Go and When
November 1, 2026
Biology
Examples of Tissues in Animals and Plants
November 1, 2026
Biology
18 Facts About Regenerative Medicine, Minus the Hype
November 1, 2026
Chemistry
Uses of Uranium: From Power Plants to Vintage Glass
November 1, 2026
Before you buy
Books and gear for science readers, students and classrooms, with the specs and editions checked for every pick.
Free to print
Periodic tables, conversion charts and worksheets as free PDFs in US Letter and A4, with answer keys for the quizzes.
Weight Conversion Chart
Kilograms to pounds and pounds to kilograms for every body weight, plus ounces, grams and a units table.
Height Conversion Chart
Feet and inches to cm and cm to feet and inches, from 4 to 7 feet, with meters on every row.
Printable Periodic Table
Free periodic table PDFs in color, black and white, blank with a key, kids and an element list, plus a build-your-own customizer.
Fresh from the lab
Biology
Examples of Fertilizers, With N-P-K Values and Uses
The most common examples of fertilizers are urea, ammonium sulfate, superphosphate, potassium chloride (muriate of potash), NPK blends,…
November 1, 2026
Chemistry
Aldehydes vs Ketones: Differences, Tests, and Why
TLDR Contents Differences between aldehydes and ketones at a glance Both families contain the carbonyl group, a carbon…
November 1, 2026
Geology
Minerals in Jordan: What’s Mined and Where
Jordan has almost no oil, but it sits on some of the most productive mineral ground in the…
November 1, 2026
Biology
Natural Fertilizers: What to Use, How Much, and When
A natural fertilizer is a plant nutrient source made from animal, plant or mineral material that has been…
November 1, 2026
Energy
Disadvantages of Nuclear Energy: 9 Costs Behind the Power
Nuclear power produces almost no carbon while running, yet it’s one of the hardest energy sources to build,…
November 1, 2026
Geology
Minerals in Iran: Reserves, World Rankings and Mines
Iran has one of the richest mineral endowments on Earth and one of the least developed mining sectors.…
October 26, 2026
Chemistry
Uses of Nickel: Where This Metal Actually Ends Up
TLDR Nickel is mostly an alloy metal. Roughly two-thirds of it goes into stainless steel, where it keeps…
October 26, 2026
Biology
Non-Flowering Plants: Mosses, Ferns, Conifers and More
Non-flowering plants are plants that never produce flowers. They reproduce with spores or with seeds that aren’t enclosed…
October 26, 2026
Biology
20 Facts About Frogs That Sound Fake (but Aren’t)
Frogs swallow with their eyeballs, breathe through their skin, and one species can spend winter frozen solid and…
October 26, 2026
Why we publish
33Science is an independent publication exploring the natural world — from the chemistry of a single crystal to the life cycle of a star. Clear, curious and rigorously sourced, for readers of every background.
