how to connect two different windows form application in c#

Hi i am new to c# i am making hospital database management system.i am working on four different department laboratory,pharmacy etc

what i want is to connect two different window form application.For example on my reception department which is window form application 1 i want to call the forms of window form application 2 on window form application 1.How can i do this

plx help as soon as possible.