There are multiple definitions:

1. one-photon microscopy(English)

   • uses a single photon of higher energy to excite the fluorophore
   • TPM
   • Microscopy, Photonics
   • https://doi.org….1021/ar800185u

2. Office of Personnel Management(English)

   • may refer to USA White House
   • Organization (management), Organizations (governmental)
   • https://www.fed…?et_cid=5596067