Although the word “metaphysics” goes back to Aristotelean philosophy, Aristotle himself credited earlier philosophers with dealing with metaphysical questions.
Scientific questions in ancient Greece were addressed to metaphysicians, but by the 18th century, the skeptics’ How do you know? led to a new branch of philosophy called epistemology (how we know) to fill-out the metaphysics (what we know) and this eventually led to science (Latin, knowledge of) and its scientific method.
Science, a branch of philosophy based on a standard of comparison, of measurement, leading to a generalized and reasoned conclusion regarding the natural world, with a high rate of reproducibility to support the claim.
Skepticism evolved epistemology out of metaphysics.
Thereafter, metaphysics denoted philosophical inquiry of a non-empirical character into the nature of existence.
Since the beginning of modern philosophy during the seventeenth century, problems that were not originally considered within the bounds of metaphysics have been added to its purview, while other problems considered metaphysical for centuries are now typically subjects of their own separate regions in philosophy, such as philosophy of religion, philosophy of mind, philosophy of perception, philosophy of language, and philosophy of science.
In some cases, subjects of metaphysical scholarship have been found to be entirely physical and natural, thus making them part of science proper (cf. the theory of Relativity).