* Historically: Many early scientists were self-taught or had relatively little formal education by today's standards. Think of figures like Leonardo da Vinci or Isaac Newton, whose scientific achievements were largely independent of formal university programs as we know them.
* 19th and early 20th centuries: A university education became increasingly important, with many scientists earning bachelor's and master's degrees. A PhD (Doctor of Philosophy) became the standard for advanced research, though not universally required.
* Modern Era (late 20th century - present): A PhD is now the almost-universal requirement for conducting independent research in most scientific fields. Many scientists then pursue postdoctoral research positions (postdocs) for several years to gain further experience and expertise before securing permanent academic or industry positions. Some scientists also hold MDs (Medical Doctor) or other professional degrees in addition to or instead of a PhD, depending on their field.
In short: While a university education, often culminating in a PhD, is now the norm for scientists, the educational path has varied greatly throughout history. The specific requirements and typical level of education also vary considerably across scientific disciplines. For example, a physicist might have a more theoretical background than a biologist, whose training might involve a lot more hands-on laboratory work.