Microscopically means in a way that's so tiny you'd need a microscope to see it, or in a way that examines something with extreme, careful attention to the smallest details.

When scientists study cells microscopically, they use powerful microscopes to see structures invisible to the naked eye. A biologist might examine pond water microscopically and discover dozens of microscopic creatures swimming around that looked like plain water before. Without microscopic examination, we'd never know about bacteria, the cells that make up our bodies, or the tiny crystals that form snowflakes.

The word also describes examining anything with intense, detail-focused scrutiny. If your teacher reviews your essay microscopically, she's checking every word choice, every punctuation mark, and every argument. When archaeologists study ancient artifacts microscopically, they might discover tool marks or traces of paint that reveal how people lived thousands of years ago.

You might hear someone say a difference between two things is microscopically small, meaning the difference exists but is almost impossible to detect, or that something changed microscopically, meaning it changed by such a tiny amount that most people wouldn't notice. The word always suggests paying attention to details that most people would overlook or couldn't see without special tools or exceptional focus.