Spores are strong resistant capsules, which are formed by bacterial cells of genus Bacillus and Clostridium only. Spores contain all vital structures of the microorganisms. In dry, cold or hot environment, where the bacterial cell will be destroyed, the spore has a much stronger resistance against such adverse conditions. The spores remain dormant (without growth) as long as the unfavourable conditions prevail. Under more favourable conditions (sufficient water/humidity and temperatures in the range of 10-40°C), spores will transform again into vegetative bacterial cells capable of multiplying and fast growing to high numbers, which can spoil and/or intoxicate food.