Abstract: Provided herein are methods of preserving a biological sample on a first substrate, the methods including: (a) disposing a biological sample on a first substrate; (b) delivering a spacer agent to the first substrate, wherein the spacer agent is applied around the biological sample on the first substrate, thereby generating a chamber around the biological sample; (c) delivering a mounting agent to the chamber; and (d) assembling the first substrate with a second substrate, thereby preserving the biological sample on the first substrate.