Cirrus clouds are ubiquitous in Earth atmosphere and as high altitude clouds usually the first solid matter that solar radiation is encountering. They have an important role in Earth’s energy balance, yet our understanding of the magnitude and even the sign of the cirrus cloud radiative effect is still under debate. One reason for this is the complicated nature of cirrus cloud building blocks: cirrus ice crystals. In this presentation, a detailed view of cirrus ice crystal morphology is given. Ice crystal morphology is then linked through light scattering theory to the cirrus global radiative effect.