# Visualize motion with marker atoms

Marker atoms in a deforming crystal

Marker atoms can be used to make the internal deformation in a solid visible as shown in the example on the right. Another possible application is tracking diffusing particles in a fluid over the course of a simulation.

The example animation has been created as follows:

1. First we apply the Slice modifier at frame 0 of the simulation (the initial state) to select a stripe of atoms. Activate the modifier's Create selection option to let the modifier select the atoms instead of deleting them.

2. We then apply the Freeze property modifier and choose the `Selection` particle property as the one to be frozen. The modifier automatically takes a snapshot of the particle selection state generated by the Slice modifier and preserves it over time.

3. Finally the Assign color modifier is used to assign a special marker color to the selected particles.