The paper presents a review of the observational investigations of the diffuse interstellar bands (DIBs) which, despite being the object of considerable research, remain unidentified since 1921. The review is focused on the most recent investigations done with the aid of solid-state detectors which make it possible to obtain high S/N spectra. It is shown that DIBs may be divided into three (or more) families probably caused by different agents. The observed profiles are usually altered by Doppler splitting when reddened stars are observed through several clouds. Also, single clouds may differ considerably in their optical properties. The paper presents 'intrinsic' (i.e., originating in single clouds) high-resolution profiles of several DIBs. These profiles are not dependent on the structure of the interstellar medium toward the observed objects.