Biopsy tissue storage. Gloved hand holding a frozen tissue sample (biopsy) in its holder, after it has been frozen in liquid nitrogen (flask in background at lower left). The white square is ice that has frozen around the actual tissue sample (pink dot) to preserve it for future examination. Biopsies are examined to help diagnose the exact nature of a patient's condition. This biopsy is one of several obtained from the knee of a patient who has rheumatoid arthritis. These biopsies were obtained by an arthroscope, a type of endoscope that is used to look inside joints. Photographed in the UK.