A port for use with a bioreactor vessel comprising: i) a base member comprising a hollow tubular portion and a base plate configured to be sealingly affixed to a hole in the wall of a bioreactor vessel ii) a hollow, generally tubular bushing member for containing electrical, optical, microfluidic and/or chemical monitoring components which bushing member fits inside the bore of the tubular portion of the base member, both the base member and bushing member providing access to the contents of a bioreactor by; iii) a monitoring assembly inserted into the bushing member which assembly comprises means for providing incoming optical and/or electrical signals and means for collecting and transmitting measurement signals resulting from the interaction of incoming optical and/or electrical signals with the contents of a bioreactor; and iv) a cover which maintains the position and alignment of components ii) and iii) relative to the base member.