foam; advances in methods for recycling of waste products (such as paper, glass, and aluminum). Genetically engineered crops are developed for commercial use. Discovery of dark matter, dark energy, brown dwarfs, and first confirmation of black holes. The Galileo probe orbits Jupiter, studying the planet and its moons extensively. Comet Shoemaker–Levy 9 (formally designated D/1993 F2, nicknamed String of Pearls for its appearance) was a comet that broke apart and collided with Jupiter in July 1994, providing the first direct observation of an extraterrestrial collision of solar system objects. The Global Positioning System (GPS) becomes fully operational. Proof of Fermat's Last Theorem is discovered by Andrew Wiles. Construction started in 1998 on the International Space Station. Society The 1990s represented continuing social liberalization in most countries, coupled with an increase in the influence of capitalism, which would continue until the Great Recession of the late 2000s/early 2010s. Youth culture in the 1990s responded to this by embracing both environmentalism and entrepreneurship. Fashion of the Western world reflected this by often turning highly individualistic and/or counter-cultural, which was influenced by Generation X and early millennials: tattoos and body piercings gained popularity, and "retro" styles, inspired by fashions of the 1960s and 1970s, were also prevalent. Some young people became increasingly involved in extreme sports and outdoor activities that combined embracing athletics with the appreciation of nature. In 1990 the World Health Organization removed homosexuality from its list of diseases. Increasing acceptance of openly homosexual people occurred in the western world, slowly starting in the early 1990s, Biphobia towards bisexual men became somewhat fashionable amongst heterosexual women and gay men, while lesbians and bisexual women complained of being commodified by publishing and film industries to cater to heterosexual men. Following the murder of actor Rebecca Schaeffer by a stalker, America's first anti-stalking laws, including California Penal Code 646.9 were passed in 1990. California also passed the first cyberstalking law in 1999 (§646.9 of the California Penal Code). Transdisciplinarity in academia. The 1st World Congress of Transdisciplinarity, Convento da Arrabida, was in Portugal, November 1994. Child abduction warnings on emergency broadcasting systems, such as Amber Alerts became standard in such cases. Midlife crisis is a major concern in domestic violence, social implications and suicides for middle-aged adults in the 1990s. Aggressive marketing tactics for psychotropic drugs and drugs used to treat Attention deficit hyperactivity disorder, inappropriate prescribing by doctors. Environment At the beginning