Life on Earth emerged in highly radioactive environment, however after years of transformation, radiation doses have significantly decreased on the surface of our planet. In such low-dose conditions we have been living for ages, until now. Actually, space is no limit, we travel to deep space, outside protective magnetic shield. We go to the Moon, to Mars and beyond. What are main challenges and risks there, with particular emphasis on genetics, development, teratology and cognition? Let's look closer to the most critical parameter for life in space.