David Baltimore was an eminent virologist who was born on March 7, 1938 in New York and died on September 6, 2025 at the age of 87 from cancer. In 1970, independently of Howard Temin, he discovered the enzyme reverse transcriptase, which allows the transcription of RNA viruses into DNA, thus explaining the mechanism of replication of retroviruses and their role in the development of cancer. This discovery was revolutionary because it challenged the previous dogmas of molecular biology about the one-way flow of genetic information. For this significant contribution, he received the Nobel Prize in Physiology or Medicine in 1975 together with Temin and Renato Dulbecco. Reverse transcriptase has become the basis for the development of AIDS treatments, cancer vaccines, and many molecular biology techniques such as PCR. Baltimore also created a classification system for viruses according to their genome type and replication method. During his career, he also devoted himself to immunology and cell biology, with his research significantly influencing virology, oncology and biotechnology.