Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE Research_Staff ( employer_organisation_id VARCHAR )
TABLE: CREATE TABLE Organisations ( organisation_type VARCHAR, organisation_id VARCHAR )

### Question ###
Which organisation type hires most research staff?

### Accurate SQL ###

SELECT T1.organisation_type FROM Organisations AS T1 JOIN Research_Staff AS T2 ON T1.organisation_id = T2.employer_organisation_id GROUP BY T1.organisation_type ORDER BY COUNT(*) DESC LIMIT 1