Please note that any employment is only permitted with a suitable work permit*! This also includes research without a contract of employment.
If you can generally enter Germany visa-free, in the relevant cases you still need to apply for a visa, or you can only begin your work or research after a work permit has been issued in Germany.
*Exceptions apply only for stays of no more than 90 days for nationals of the following countries: Australia, Canada, Israel, Japan, South Korea, New Zealand, United Kingdom of Great Britain and Northern Ireland and the United States of America.
