Cross-linking is a process where two or more molecules are connected through chemical bonds. This technique is commonly used in various fields, including biology and materials science, to enhance the properties of substances. For example, in the production of polymers, cross-linking can improve strength and durability, making materials more resistant to heat and chemicals. In biological systems, cross-linking can occur between proteins or DNA strands, influencing their structure and function. This is important in processes like cell signaling and gene regulation. Overall, cross-linking plays a crucial role in both synthetic materials and natural biological functions.