Optics: spectra of various stars, including our sun. Coloured process print by Cassell. https://www.rawpixel.com/image/13957739/image-stars-sun-circleFree Image from public domain licenseNational Institute of Diabetes & Digestive & Kidney Diseases. Original public domain image from Flickr https://www.rawpixel.com/image/9647173/image-background-medicine-phoneFree Image from public domain licenseMARC: Training Biomedical Scientists for the 21st Century. Original public domain image from Flickr https://www.rawpixel.com/image/9648681/image-art-medicine-abstractFree Image from public domain license