Light detection and ranging (lidar) provides active optical remote sensing in backscattering. Lidar technique is well established, for many years, for atmospheric, meteorological and air quality applications. Recent advantages in laser and optical filters technologies allowed lidar to be more cost effective and to be used operationally. More sophisticated lidars are manufactured by researchers and companies for a big variety of studies. However, many technological challenges are still there, need special attention and will be discussed. Deferent types of lidar setups for different applications will be presented along with their advantages and disadvantages. Finally, the synergies of lidars with other techniques will be presented.