Referencing Tables In Nested Select Statements

I'm just wodnering if you have two select statements, one nested inside another, can you reference tables from the outer loop?

for example, say I would like to find all employees who have at least two clients and employees and clients have a one to many relationship.

select *
from Employee e
where
(
select count(*)
from Clients c
where c.EmployeeId = e.EmployeeId
) >= 2

This obviously doesn't work - but how would i go about doing something like this?