Access our award-winning, free resources for teaching and learning science.

About us

We create and provide high-quality, accessible, educational content in the science, technology, engineering and mathematics (STEM) disciplines at the introductory undergraduate level.

Learn More
We support NGSS

Our exclusive content integrates science and engineering practices with disciplinary core ideas and cross-cutting concepts in alignment with the Next Generation Science Standards.

Learn More

Quick Quiz

Density is defined as

Go to Quiz

Module of the day

Description in Scientific Research

Observation is an important tool for scientific researchers, and describing what is observed is a valuable method of research. This module…

Go to module

Term of the day


[adjective] Having a regular, lattice-like arrangement of atoms or molecules. Crystalline solids melt at a precise melting point and break along specific…

Go to term