**1. Introduction**

The development of chemosensors has been the subject of intensive research for potential applications in various fields covering human health, industries, and security fields. Gas chromatography, high-performance liquid chromatography, and electrochemical sensing are commonly used for the detection of small molecules and volatile organic compounds. However, most of these methods fail to meet the requirements of simple operation and are expensive. In this context, vapochromic materials that undergo color and/or fluorescence changes in response to specific gases and vapors have been a promising phenomenon. Colorimetric sensor arrays with pattern recognition capabilities have been widely used to detect and discriminate multiple chemically similar samples.

In the last decades, vapochromic materials based on organic dyes, metal complexes, metal organic frameworks, and covalent organic frameworks have attracted a lot of attention and various researches have been carried out. Various metal complexes are known to show vapochromism in the solid-states due to the significant changes in the metal-to-metal interaction and coordination bonding modes caused by the adsorption and desorption of vapor molecules. Several examples of metal-containing vapochromic materials such as Pt(II) or Au(I) have been reported and compiled in review papers [1–6]. On the other hand, metal-free vapochromic materials have been recently considered. The purpose of this mini-review is to investigate recent advances in the fields of vapochromism/vapofluorochromism of organic materials, especially focusing on host–guest compounds with distinct mechanisms and where structural identification has been achieved.
