Alex presents an invited talk at the 10th edition of the conference of the Asia Pacific Association of Theoretical and Computational Chemistry (APATCC-10) which took place in the unique conference site of the International Centre for Interdisciplinary Science and Education (ICISE), Quy Nhon, Vietnam, from 19 to 23 February 2023. Alex’s talk was titled “Two- and three-photon absorption in fluorescent proteins and their chromophores.”