A sample container was a usually cylindrical container used by the Federation to hold matter or energy for scientific study. They came in a variety of specifications, and could be reinforced with a containment field.
In 2151, Crewman Cutler sterilized sample containers for the Enterprise NX-01's away mission to Archer IV. (ENT: "Strange New World")
In 2369, a USS Enterprise-D away team discovered fragments of a standard sample container on the transporter pad of the disabled USS Yosemite. By replicating the accident, they learned that the Yosemite crew had taken a sample from a plasma streamer, not knowing that it contained quasi-energy microbes. When they performed a resonance frequency scan on the sample, the microbes shattered the container. (TNG: "Realm Of Fear")
In 2371, the USS Voyager crew collected two samples of photonic matter from a protostar. The samples were in fact photonic lifeforms, one of which broke through its container and escaped the ship when it was subjected to a polarization field. The other was released from its container by the Doctor. (VOY: "Heroes and Demons")
Later that year, the Voyager crew beamed a sample of the metreon cloud over Rinax into a container for Doctor Ma'Bor Jetrel's experiments in restoring the victims of the metreon cascade. (VOY: "Jetrel")
In 2372, Lieutenant Tuvok and Neelix collected several dozen symbiogenetic alien orchids, which were in sample containers on their persons when they beamed back to Voyager. The orchids caused a transporter accident that merged them into Tuvix. (VOY: "Tuvix")
In 2374, the Voyager crew attempted to beam deuterium from the surface of a class Y planet into a container. However, the pattern buffers overloaded and destroyed the container. (VOY: "Demon")
For anomaly consolidation duty on the USS Cerritos in 2381, many of the specimens earmarked for disposal were housed in sample containers, including a frog skull and a slug. Many of these were poorly contained; a number of nanobots that Lieutenant Commander Andy Billups had been using fell out of their container when it was knocked down due to Billups' failure to tighten the lid properly. Others, including a plant that sprayed thorns into Ensign Beckett Mariner's face, were placed in containers by Ensigns Mariner, D'Vana Tendi, and Sam Rutherford. (LD: "The Spy Humongous")