Welcome to this special section honoring the scientific career of Michael Feld. We, the guest editors, have been heartened by the tremendous response from the biomedical optics community regarding this special section. As a long-time colleague (Dasari) and former graduate students (Richards-Kortum and Berger), we are grateful that so many other colleagues and students of Michael's have elected to contribute their latest results to this forum in Michael's honor.

This special section begins with a biographical sketch written by Dr. Charles Holbrow, a colleague of Michael Feld's dating back several decades. While this piece captures many details of a remarkable scientist's career, it also provides some splashes of the color that made Michael a unique colleague, mentor, conference attendee, and friend. All three of us, along with many in the biomedical optics community today, were shaped by Michael Feld's persistence in following his instincts, his willingness to ask sharp questions, his humorous sense of irreverence, and his legendary tirelessness whenever crunch time arrived.

Like the other scientists who have been profiled in previous JBO Pioneers in Biomedical Optics special sections, Michael Feld richly deserves to be called a biomedical optics "pioneer," and not just of a single methodology. Appropriately, the contributions to this special section hail from the many corners of the biomedical optics field that he touched. Throughout Michael's biomedical work, spectroscopy was a recurrent theme, be it absorption-, fluorescence-, or Raman-based; all of these techniques are represented in this special section, often in multimodal combinations. In his later years, Michael's research group broke new ground in the analysis of elastic scattering and in quantitative phase microscopy, both of which are discussed in the contributed papers. As of this writing, 14 papers are included in all.

It has been a pleasure for us to serve as guest editors in assembling this issue. We miss Michael and hope that the research presented in this special JBO issue will serve both as a suitable memorial to Michael Feld and a continuing inspiration to those of us who follow in his footsteps.