The drive to answer ever more complex questions brings different fields of natural sciences together. Biology and photonics, for example, unite in the field of biophotonics. Both fields continuously approach each other of the last decades, as is best seen in the field of microscopy. We contribute to a better understanding of biology as we are developing and applying methods of optical micromanipulation and metrology. We use optical tweezers to stretch cells and high speed microscopy to characterize blood flow in living organisms. Both methods give insight and understanding into the state of health and development of such organisms.