Sectioning Organoids and Spheroids: What Changes at the Microtome

Your microtome was built to section tissue blocks. Nobody designed it for a spheroid smaller than a grain of sand — and yet that's increasingly what turns up on the chuck. The good news: the instrument barely has to change. Your approach does.

The way it goes wrong

Face a block too keenly and you sail straight through a sub-millimetre organoid, leaving nothing to report. On a routine biopsy you'd shrug; here it's the entire specimen gone. So the win is made before the block ever reaches the knife.

Before the microtome

Two habits do most of the work: concentrate and dye the organoids into a visible gel pellet (see organoid histology), and embed that pellet flat so everything sits in one cutting plane. Get those right and the rest is calm.

At the microtome

Face gently, in thin advances, and watch for the coloured pellet to surface. When it does, cut and mount serial levels rather than gambling everything on a single plane — depth is where tiny targets hide. Keep the block cold and firm so the ribbons come off clean, without compression.

Frozen sections too

For rapid or antigen-sensitive work, organoids can be frozen in OCT and cut on a cryostat. Same rules apply — a visible, well-oriented pellet, and patient, level-by-level cutting.

Bottom line

The machine hardly changes; the mindset does. Make the target visible, embed it flat, take levels — and a routine microtome handles organoids and spheroids without drama.