Reheating leftovers can be risky due to the potential growth of bacteria and toxins. High-protein foods, leafy greens, pre-cut fruits, cooked rice, pasta, and seafood are particularly susceptible. Proper storage and timely consumption are crucial to avoid food poisoning from pathogens like Listeria, Salmonella, E. coli, and Bacillus cereus. Always reheat to at least 165°F to ensure safety.