Biological products include vaccines, blood products, recombinant proteins, tissues, and gene therapies. They are complex mixtures isolated from living organisms and produced through biotechnology. Unlike conventional drugs, biologics have unknown structures, are heat-sensitive, and require aseptic manufacturing. Biosimilars are approved based on high similarity to a reference biologic and no clinically meaningful differences in safety or effectiveness. The Biologics Price Competition and Innovation Act established an abbreviated pathway for biosimilar approval and a process called the "patent dance" to resolve patent disputes between reference product sponsors and biosimilar applicants. This involves exchanging information and patent lists within strict timelines to determine which patents will be subject to litigation.